%0 journal article %@ 1005-0302 %A Wu, T.,Blawert, C.,Serdechnova, M.,Zheludkevich, M.L. %D 2025 %J Journal of Materials Science & Technology %N %P 30-52 %R doi:10.1016/j.jmst.2023.12.084 %T Dissimilar metal joints on macro- and micro scales: Impact on PEO processing-A review %U https://doi.org/10.1016/j.jmst.2023.12.084 %X Plasma electrolytic oxidation (PEO) processing of light metals has been established for decades and is in increasing industrial use, even as an alternative surface treatment to produce multifunctional coatings with environmental-friendly processing concept. One of the benefits of PEO processing claimed already a couple of years ago was the ability to treat dissimilar metal joints, which can obviously improve the surface homogeneity and stability at the interface of the dissimilar components, especially impeding the galvanic corrosion due to the different electrochemical properties of each component. However, the progress and breakthrough develop slowly especially for the macro scales due to the much larger gap between each component. This literature review firstly demonstrates the still low number of studies reporting successful PEO treatment of material combination such as Mg/Al, Mg/Ti, Al/Ti and scarcely light metal combinations with steel. The main issues and challenges to performing PEO processing on the macro-scale dissimilar weldments were stated. On the other hand, dissimilar metal joints also widely exist in micrometer scale in alloys and metal matrix composites (MMCs). Moreover, there is a huge knowledge base on PEO treatment of such multiphase substrates. PEO processing of such complicated mixed microstructures is reviewed as well to reveal the basic problems. To some certain degree, these PEO-related studies on alloys and MMCs can be good examples to have an insight into the coating formation mechanism on macro-scaled dissimilar metal joints. Conclusions are drawn from the micro- to macroscale. Finally, critical access to the problems is given and possible solutions and reaming limitations are discussed. %0 journal article %@ 1614-6840 %A Kim, H.,Deng, M.,Fortuin, A.,Würger, T.,Georgopanos, P.,Kramer, D.,Zheludkevich, M.,Höche, D. %D 2024 %J Advanced Energy Materials %N %P 2401266 %R doi:10.1002/aenm.202401266 %T Influence of Simple Salts on Solvent Reduction Stability at Mg-Alloy Anodes Interface: A Potential-Dependent DFT Study %U https://doi.org/10.1002/aenm.202401266 %X The significance of incorporating anion species into electrolyte solvation structures, particularly with doubly charged Mg2 + ions, is investigated using the grand canonical density functional theory (GC-DFT) approach. In an extension of previously established methodology, the work explores the thermodynamic stability in acetonitrile (AN) at the interface with Mg3Bi2 and Mg2Sn. Two different anions, TFSI− and,ClO4-, are strategically incorporated based on energy comparisons. Despite the known chemical compatibility of alloy anodes with the electrolyte solution, the research reveals a novel form of solvent degradation, which is also reported in the case of pure Mg anode with conventional electrolytes. Notably, the AN molecule adjacent to anion species exhibits reduced susceptibility to reduction (−0.8 – −0.4 V vs Mg2 +/Mg) in the lower potential range in comparison with the solvation structure of full dissociation. Charge density difference and density of states analyses detail solvent molecules becoming electrophilic, with the LUMO overlapping with the Fermi level at lower potentials when the electrostatic interaction with anion species are considered. Experimental studies using nuclear magnetic resonance (NMR) spectroscopy and linear sweep voltammetry (LSV) validate the theoretical results, providing a comprehensive understanding. This methodology, augmenting prior approaches, provides valuable guidance for electrolyte composition based on predominant solvation structures in multivalent solutions. %0 journal article %@ 2397-2106 %A Özkan, C.,Sahlmann, L.,Feiler, C.,Zheludkevich, M.,Lamaka, S.,Sewlikar, P.,Kooijman, A.,Taheri, P.,Mol, A. %D 2024 %J npj Materials Degradation %N %P 21 %R doi:10.1038/s41529-024-00435-z %T Laying the experimental foundation for corrosion inhibitor discovery through machine learning %U https://doi.org/10.1038/s41529-024-00435-z %X Creating durable, eco-friendly coatings for long-term corrosion protection requires innovative strategies to streamline design and development processes, conserve resources, and decrease maintenance costs. In this pursuit, machine learning emerges as a promising catalyst, despite the challenges presented by the scarcity of high-quality datasets in the field of corrosion inhibition research. To address this obstacle, we have created an extensive electrochemical library of around 80 inhibitor candidates. The electrochemical behaviour of inhibitor-exposed AA2024-T3 substrates was captured using linear polarisation resistance, electrochemical impedance spectroscopy, and potentiodynamic polarisation techniques at different exposure times to obtain the most comprehensive electrochemical picture of the corrosion inhibition over a 24-h period. The experimental results yield target parameters and additional input features that can be combined with computational descriptors to develop quantitative structure–property relationship (QSPR) models augmented by mechanistic input features. %0 journal article %@ 1226-086X %A Kasneryk, V.,Wu, T.,Rohr, H.,Serdechnova, M.,Mojsilovi , K.,Wieland, F.D.C.,Davydok, A.,Gazenbiller, E.,Vasili , R.,Blawert, C.,Stock, N.,Zheludkevich, M.L. %D 2024 %J Journal of Industrial and Engineering Chemistry %N %P 119538 %R doi:10.1016/j.jiec.2023.11.033 %T Controllable recrystallization of ZnO/ZnAl2O4 based PEO into ZIF-8 as a route for the formation of multifunctional coatings %U https://doi.org/10.1016/j.jiec.2023.11.033 %X Nowadays, plasma electrolytic oxidation (PEO) has become widespread as an effective method for preparation of multifunctional coatings. However, the PEO coatings have numerous pores. On the one hand, their presence restricts their broad application; on the other hand, they represent an excellent platform for post-sealing allowing creating coatings with peculiar properties. In the current work, the possibility of controllable recrystallization of ZnO/ZnAl2O4 based PEO preformed on Zn Z1 alloy into ZIF-8@PEO composite coating was demonstrated for the first time. It was found that the corrosion protection, photocatalytic and photoluminescence properties of the final coatings can be modified by varying the conditions of the post-modification process, which include the amount of the organic linker (2-methylimidazole) and treatment time. This study opens an innovative approach for the formation of multifunctional coatings. %0 journal article %@ 0010-938X %A Vaghefinazari, B.,Lamaka, S.V.,Gazenbiller, E.,Yasakau, K.,Blawert, C.,Serdechnova, M.,Scharnagl, N.,Wieland, D.C.F.,Zheludkevich, M.L. %D 2024 %J Corrosion Science %N %P 111651 %R doi:10.1016/j.corsci.2023.111651 %T Corrosion inhibition of decylphosphonate on bare and PEO-coated Mg alloy %U https://doi.org/10.1016/j.corsci.2023.111651 %X PEO coatings, aside from their reasonable corrosion protection, also feature a porous microstructure that can serve as a repository for corrosion inhibitors. This study presents and investigates the high corrosion inhibition effect of sodium salt of decylphosphonate (DP) when incorporated into PEO coating on a magnesium substrate. The interaction of DP with both bare and PEO-coated magnesium substrates was studied to understand its corrosion inhibition mechanism. Additionally, a strategy to enhance the active anti-corrosion ability of the DP-containing system was suggested and examined. The findings provide new insights into the potential of surfactants as corrosion inhibitors for magnesium alloys. %0 journal article %@ 2468-0230 %A Yeshmanova, G.,Blawert, C.,Serdechnova, M.,Wieland, F.D.C.,Starykevich, M.,Gazenbiller, E.,Höche, D.,Smagulov, D.,Zheludkevich, M.L. %D 2024 %J Surfaces and Interfaces %N %P 103797 %R doi:10.1016/j.surfin.2023.103797 %T Effect of electrolyte composition on the formation of PEO coatings on AA2024 aluminium alloy %U https://doi.org/10.1016/j.surfin.2023.103797 %X Since the electrolyte composition plays a crucial role in the plasma electrolytic oxidation (PEO) coating formation process, a systematic and in-depth study was proposed to identify an electrolyte composition for fast PEO coating growth on AA2024 alloy. Different concentration ratios of mixed alkaline electrolytes (hydroxide, silicate and phosphate) were investigated. PEO process was conducted at low constant current density of 50 mA/cm2, which is intended for lowering the energy consumption. Results demonstrated that the breakdown voltage of PEO coatings is directly proportional to the logarithm of electrolyte resistivity. The coating growth mechanism showed two main directions. The thickening of the coating mainly depends on the rapid deposition of electrolyte compounds in Si-based electrolyte, and the coating growth occurs mainly towards the electrolyte/coating interface. Contrary, in OH-, and P-based electrolytes, the inward coating growth was dominating mainly by substrate oxidation. A variety of phases as a function of different electrolyte compositions and final voltages were observed. With high final voltages (over 470 V) for coatings produced in mixed electrolytes with low concentrations of hydroxide, silicate or phosphate (2 and 6 g/L), γ-Al2O3 crystalline phase predominates in the PEO layer composition. However, only a low efficiency of coating growth can be reached. In the electrolytes with high silicate concentrations accompanied by an increase of phosphate concentration, the final voltage is around 455 V and the coating composition is dominated by an amorphous phase in combination with crystalline mullite and γ-Al2O3. High silicate-phosphate contents (18–24 g/L) in mixed electrolytes with low final voltages of about 360 V results in a fully amorphous PEO layer and significantly increases coating thickness. A combination of low content of hydroxide, high silicate with increasing content of phosphate in mixed electrolyte increases the coating thickness, and improves the density and uniformity of the overall PEO layers. %0 journal article %@ 0010-938X %A Liu, M.,Zhang, Q.,Tang, X.,Liu, C.,Mei, D.,Wang, L.,Zhu, S.,Zheludkevich, M.L.,Lamaka, S.,Guan, S. %D 2024 %J Corrosion Science %N %P 111851 %R doi:10.1016/j.corsci.2024.111851 %T Effect of medium renewal mode on the degradation behavior of Mg alloys for biomedical applications during the long-term in vitro test %U https://doi.org/10.1016/j.corsci.2024.111851 %X To build a suitable corrosion environment for testing the degradation behavior of magnesium alloy in vitro, the medium and test environment are constantly optimized. However, the applicability of medium renewal mode is still vague. In this study, based on three representative test protocols, the influence of the specific ratio of media volume to surface area and the disposable medium real-time renewal mode (flow-through) on Mg corrosion were investigated. It is found that in flow-through medium renewal mode, the composition of the medium is maintained quasi-constant which is essential for corrosion tests. The selection suggestion on medium renewal mode was also proposed. This work is beneficial for ultimately establishing the representative in vitro testing protocols for Mg bioabsorbable materials. %0 journal article %@ 0010-938X %A Song, C.,Wang, C.,Mercier, D.,Vaghenfinazari, B.,Seyeux, A.,Snihirova, D.,Wieland, F.D.C.,Marcus, P.,Zheludkevich, M.L.,Lamaka, S.V. %D 2024 %J Corrosion Science %N %P 111867 %R doi:10.1016/j.corsci.2024.111867 %T Corrosion inhibition mechanism of 2,6-pyridinedicarboxylate depending on magnesium surface treatment %U https://doi.org/10.1016/j.corsci.2024.111867 %X 2,6-pyridinedicarboxylate (2,6-PDC) was studied as corrosion inhibitor for pure magnesium. The surface was prepared either by polishing or polishing followed by treatment with 1 M NaOH solution. The results show that 2,6-PDC promotes the formation of a denser protective oxide/hydroxide layer poor in PDC. The mechanism proposed includes forming weak PDC-Mg complexes that lower the free Mg2+ concentration available for the formation of Mg(OH)2. This leads to growth of smaller Mg(OH)2 platelets that are more densely packed and hence form a more protective layer. The highest inhibition efficiency of 2,6-PDC was achieved for samples with surface hydroxylated by NaOH treatment. %0 journal article %@ 1944-8244 %A Zhang, Z.,Wang, J.,Serdechnova, M.,Kasneryk, V.,Blawert, C.,Wang, H.,Zheludkevich, M.L.,Chen, F.,Zhang, Y. %D 2024 %J ACS Applied Materials and Interfaces %N 9 %P 11944–11956 %R doi:10.1021/acsami.3c19432 %T An inhibitor-loaded LDH and MOF-based bilayer hybrid system for active corrosion protection of aluminum alloys %U https://doi.org/10.1021/acsami.3c19432 9 %X A novel inhibitor-loaded bilayer hybrid system based on the LDH inner layer and MOF outer layer is designed on an aluminum alloy 2A12 surface to improve corrosion performance. The hybrid film system covers the inherent cavities and intercrystalline defects of the LDH film using the affinity between the LDH and the MOF compounds. The results demonstrate that the LDH-inhI precursor film is entirely covered by new Zn-based MOF microrods. The LDH-inhI precursor film is partially dissolved and recrystallized in favor of MOF crystal growth to strengthen the binding adhesion between LDH and MOF films. The LDH-inhI/MOF-inhII bilayer film shows significantly enhanced corrosion resistance through the synergistic action of LDH and MOF nanocontainers doped with different corrosion inhibitors (vanadates, 2,5-furandicarboxylic acid, and benzotriazoles). Due to the multiple loadings of the MOF film and the sustained-release of the LDH film, this method provides an effective approach to developing new anticorrosion systems and enhancing both the barrier ability and active corrosion protection performance of LDH-based conversion treatments. %0 journal article %@ 0169-4332 %A Mojsilović, K.,Serdechnova, M.,Blawert, C.,Zheludkevich, M.L.,Stojadinović, S.,Vasilić, R. %D 2024 %J Applied Surface Science %N %P 159450 %R doi:10.1016/j.apsusc.2024.159450 %T In-situ incorporation of LDH particles during PEO processing of aluminium alloy AA2024 %U https://doi.org/10.1016/j.apsusc.2024.159450 %X The preparation and properties of oxide coatings obtained by plasma electrolytic oxidation in close to pH-neutral titanium oxide oxalate K2TiO(C2O4)2 electrolyte on aluminum AA2024 have been investigated and discussed. Immobilization of different Zn-Al layered double hydroxides (LDH) have been tested: LDH[CO3] and LDH[MBT]. LDH[CO3] was also tested with 2-mercaptobenzothiazole (MBT) as an additive to the PEO electrolyte. Obtained coatings are characterized with respect to their morphology, phase and chemical composition, photocatalytic activity and anti-corrosion properties. Obtained PEO coatings show typical PEO morphology, except a particular foamy structure achieved for coatings in LDH[MBT]-containing electrolyte, allowing interesting possible applications, particularly in the field of photocatalysis. All coatings contain elements originating from both the substrate and the electrolyte, with EDS analysis displaying a prominent presence of Ti, and the presence of Zn originating from LDH addition to standard electrolyte. XRD patterns of formed PEO coatings reveal the changing ratio of anatase-to-rutile, but with additional formation of crystalline phases such as K0.12Ti8O16, Ti5O9, Ti2O3, γ-Al2O3 and ZnAl2O4. Despite a standard PEO surface morphology, the highest photocatalytic activity reaching 52 % is observed for coatings created in LDH[CO3]-containing electrolyte. Notable anti-corrosion properties were achieved for coatings with LDH[CO3] and MBT added to the electrolyte. %0 journal article %@ 0947-6539 %A Tsimafeyeva, K.A.,Starykevich, M.,Snihirova, D.,Blawert, C.,Scharnagl, N.,Schuster, A.,Gavras, S.,Luthringer-Feyerabend, B.J.C.,Zheludkevich, M.L. %D 2024 %J Chemistry - A European Journal %N 18 %P e202303012 %R doi:doi.org/10.1002/chem.202303012 %T Characterization and In Vitro Behavior of PEO Coated Mg Modified with Antibacterial Ag(I) and Cu(II) Complexes %U https://doi.org/doi.org/10.1002/chem.202303012 18 %X The use of Mg-based biomaterials with a number of their advantageous properties are overshadowed by uncontrollable metal corrosion. Moreover, the use of implants goes alongside with the threat of pathogens-associated complications. In this study, PEO coated Mg biomaterial loaded with antibacterial Ag(I) and Cu(II) complexes is produced and tested to meet both appropriate protective characteristics as well as sufficient level of antibacterial activity. To achieve a suitable level of anticorrosion protection phosphate and fluoride-phosphate electrolytes are used in the PEO process. Investigation of the surface thickness and morphology done by means of cross-section analysis and scanning electron microscopy (SEM), as well as electrochemical impedance spectroscopy (EIS) assay show precedence of the fluoride containing PEO coating and make it the material of choice for further modification with Ag(I) and Cu(II) complexes. The presence of the complexes on the PEO surface is confirmed by energy dispersive X-ray spectroscopy (EDX). X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and glow discharge optical emission spectroscopy (GDOES) are used to estimate the complexes’ chemical state and depth of penetration in the coating surface. Based on the results of antibacterial assay, the modified coatings are found to be active against both Gram-positive and Gram-negative bacteria. %0 journal article %@ 2468-0230 %A Hejjaj, C.,Scharnagl, N.,Lamaka, S.V.,Fischer, C.B.,Zheludkevich, M.L. %D 2024 %J Surfaces and Interfaces %N %P 104098 %R doi:10.1016/j.surfin.2024.104098 %T Highly efficient anti-corrosion polyetherimide (PEI) coating encapsulated with aluminum di-hydrogen tri-polyphosphate %U https://doi.org/10.1016/j.surfin.2024.104098 %X Protective composite coatings based on polyetherimide (PEI) incorporated with aluminum di-hydrogen tri-polyphosphate (ATP) particles for the protection of carbon steel are reported here. The ATP particles were used as an inhibiting pigment. The layers were applied by the dip coating method leading to a full uniform coverage as confirmed by microscopic and Raman spectroscopy techniques. The anti-corrosion characteristics of the PEI-coated samples were investigated in a 3.5 wt.% NaCl solution by electrochemical impedance spectroscopy. The results revealed that PEI-ATP composite coating exhibited higher impedance values above 109 Ω.cm2 (up to 30 days) compared to a Blank-PEI coating. The active protection was studied by the scanning vibrating electrode technique revealing clear signs of inhibition in the artificial defects. The proposed mechanistic insights into the protective properties of PEI-ATP coating was further supported using X-ray photoelectron spectroscopy. %0 journal article %@ 2213-9567 %A Xie, P.,Blawert, C.,Serdechnova, M.,Konchakova, N.,Shulha, T.,Wu, T.,Zheludkevich, M.L. %D 2024 %J Journal of Magnesium and Alloys %N 4 %P 1386-1405 %R doi:10.1016/j.jma.2024.01.020 %T Effect of low concentration electrolytes on the formation and corrosion resistance of PEO coatings on AM50 magnesium alloy %U https://doi.org/10.1016/j.jma.2024.01.020 4 %X In this paper, the formation process, morphology, and electrochemical performance of PEO coatings on AM50 magnesium alloy prepared in low concentration phosphate, aluminate, and phosphate-aluminate electrolytes were systematically studied. The results show that the coatings prepared from the phosphate electrolytes have a higher thickness and better corrosion resistance properties compared to the other electrolytes. The coatings prepared from low concentration phosphate-aluminate mixed electrolytes have slightly thinner thickness, a similar coating structure and an order of magnitude lower value of electrochemical impedance compared with phosphate electrolyte coatings. The Coatings prepared from low concentration aluminate electrolytes have the lowest thickness and the worst corrosion resistance properties which gets close to corrosion behavior of the bare AM50 under the same test conditions. Considering application, coatings prepared from single low concentration phosphate electrolytes and low concentration phosphate-aluminate electrolytes have greater potential than single low concentration aluminate coatings. However, reducing the electrolyte concentrations of coating forming ions too much has negative influence on the coating growth rate. %0 journal article %@ 0010-938X %A Zhou, Y.,Lu, X.,Würger, T.,Höche, D.,Zheludkevich, M.L.,Wang, F. %D 2024 %J Corrosion Science %N %P 112009 %R doi:10.1016/j.corsci.2024.112009 %T New insights into the inhibition mechanism of carboxylate species on magnesium surface %U https://doi.org/10.1016/j.corsci.2024.112009 %X The microstructure and composition of corrosion film deposited on pure Mg were systematically investigated, and for the first time DFT was used to reveal the adsorption behavior of carboxylates on the surface of corrosion layer rather than the metallic Mg. Presence of carboxylate inhibitor dramatically modified composition of the corrosion film and bonded directly with Mg atoms in the outermost MgO based corrosion layer by means of carboxyl. The bonded Mg atoms were lifted by 0.8 – 1.1 Å from their original position when abundant inhibitors started to act as complexing agent, leading to deteriorated inhibition effect. %0 journal article %@ 0169-4332 %A Shulha, T.,Shikun, M.,Serdechnova, M.,Naacke, T.,Kasneryk, V.,Heitmann, V.,Karlova, P.,Davydok, A.,Karpushenkov, S.A.,Blawert, C.,Zheludkevich, M.L. %D 2024 %J Applied Surface Science %N %P 160707 %R doi:10.1016/j.apsusc.2024.160707 %T Chelating agent stimulated LDH post-treatment of PEO coated AA2024 %U https://doi.org/10.1016/j.apsusc.2024.160707 %X Layered double hydroxides (LDHs) are well known and broadly investigated on bare aluminum alloys, but not on PEO treated aluminum where source of aluminum ions is restricted. The additions of the chelating agents were tested in this work to stimulate the LDH formation on PEO (plasma electrolytic oxidation) coated aluminum alloy AA2024. 1,3-diamino-2-hydroxipropane-N,N,N’,N’-tetraacetic acid (DHPTA) was identified as the most effective one among tested additives. Its performance in terms of LDH growth stimulation was investigated. The DHPTA additive provides an increase of the pH of the LDH synthesis compared to previously known methods to achieve hydration of aluminum oxide from PEO as the initial stage of PEO etching, as well as the formation of soluble complex compounds of Zn-DHPTA, necessary for the formation of ZnAl LDH. The process of LDH formation was also followed by intercalation of DHPTA ions into LDH galleries. It was shown that LDH was formed both on the surface and insight the pores of parental PEO coating. Moreover, it imparted lubricating properties to the hybrid coating. Finally, PEO-LDH coating demonstrated higher corrosion resistance and long-term stability comparing to the PEO coated aluminum alloy. %0 journal article %@ 0257-8972 %A Chen, Q.,Lu, X.,Serdechnova, M.,Wu, T.,Kasneryk, V.,Naacke, T.,Wieland, D.C.F.,Blawert, C.,Zhang, Y.,Xu, Y.,Zheludkevich, M.L.,Wang, F. %D 2024 %J Surface and Coatings Technology %N %P 130907 %R doi:10.1016/j.surfcoat.2024.130907 %T Insights into in-situ synthesis of PEO-LDH composite film on AM50 Mg alloy: The effect of final voltage %U https://doi.org/10.1016/j.surfcoat.2024.130907 %X Mgsingle bondAl layered double hydroxide (LDH) layer was in-situ grown on PEO coatings formed at different voltages. Influence of thickness, phase composition and stability of the initial PEO coating on LDH formation was investigated. A PEO layer consisting of thin and unstable amorphous phase can be recrystallized into LDH, while a dense coating slows down LDH growth. Balancing the dissolution of the PEO structure with formation of LDH nanocontainers can dramatically enhance the corrosion resistance of the resultant coating. The superior corrosion properties can be attributed to the intact parent PEO layer, the uniform coverage of the LDH film and its ion-exchange effect. %0 journal article %@ 2213-9567 %A Xu, W.,Deng, M.,Snihirova, D.,Wang, L.,Wu, Y.,Lamaka, S.V.,Zheludkevich, M.L.,Höche, D. %D 2024 %J Journal of Magnesium and Alloys %N %P %R doi:10.1016/j.jma.2024.02.011 %T A combined computational/experimental study of anode-concerned voltage drop in aqueous primary Mg-air batteries %U https://doi.org/10.1016/j.jma.2024.02.011 %X The voltage drop appearing at Mg anode-electrolyte interface is a critical issue for the battery power and energy density of aqueous primary Mg-air batteries. The respective voltage loss is typically assigned to the deposits layer forming on the anode surface during discharge. In this work, we experimentally and computationally investigate the critical factors affecting the voltage drop at Mg anode towards a deeper understanding of the contribution of deposit and its growth. A two-dimensional (2D) mathematical model is proposed to compute the voltage drop of Mg-0.15Ca wt.% alloy (Mg-0.15Ca) by means of a semi-empirical formulas and experiments-based modification model, considering the effect of discharge current density, the negative difference effect (NDE) and surface deposits layer itself. This model is utilized to simulate the discharge potential of the anode at predefined experimental current densities. The computed voltage drop (half-cell voltage) is in good agreement with the experimental value. The applicability of the mathematical model is successfully validated on the second material (namely high-purity Mg). %0 journal article %@ 2238-7854 %A Blawert, C.,Serdechnova, M.,Bertram, J.,Momber, A.,Konchakova, N.,Höche, D.,Zheludkevich, M.L. %D 2024 %J Journal of Materials Research and Technology : JMRT %N %P 844-859 %R doi:10.1016/j.jmrt.2024.06.097 %T Effects of mechanical surface pre-treatment on integrity and corrosion of bare and coated AA6082 substrates %U https://doi.org/10.1016/j.jmrt.2024.06.097 %X In this study, two classes of surface pre-treatment methods, namely three blast-cleaning methods with different abrasive materials (for initial preparation) and three mechanical methods (for repair applications) were applied to study their effects on surface morphology, composition, and corrosion of AA6082 substrates in artificial seawater. Coating adhesion and coating corrosion protection ability were investigated by applying a single-layer epoxy coating (250 μm dry film thickness) onto the substrates.,The mechanical methods delivered cleaner surfaces with more regular surface morphologies, whereas the blast-cleaning methods revealed less clean surfaces and more irregular surface morphologies. The latter methods promoted the detrimental embedment of abrasive particles into the substrates. The corrosion performance of the pre-treated substrates was worse after blast-cleaning compared to mechanical treatments. However, all methods met the adhesion requirements for offshore applications. Regarding coating degradation, only the filiform corrosion test delivered meaningful results, whereas the duration of the cyclic corrosion test (3000 h) was too short to distinguish between the different methods because of neglectable degradation. Mechanical interlocking and isotropic surface morphologies are found to be more important for coating performance than a cleaner surface, and the remains of blasting material were neglectable too. %0 journal article %@ 0169-4332 %A Stephan, J.,Kasneryk, V.,Serdechnova, M.,Scharnagl, N.,Gazenbiller, E.,Vaghefinazari, B.,Volovitch, P.,Starykevich, M.,Blawert, C.,Zheludkevich, M.L. %D 2024 %J Applied Surface Science %N %P 159919 %R doi:10.1016/j.apsusc.2024.159919 %T Formation of Li-Al LDH conversion layer on AA2024 alloy for corrosion protection %U https://doi.org/10.1016/j.apsusc.2024.159919 %X AA2024 aluminium alloy is widely used in the aerospace industry. However, it is known to be highly susceptible to localised corrosion, which is related to its complex microstructure, mainly the presence of numerous Cu-rich intermetallic particles. One of the effective solutions to increase their corrosion resistance relies on the formation of layered double hydroxide (LDH) based conversion coatings (CC). This investigation aims to understand how the conditions of in situ Li-Al LDH-CO32-/OH– CC growth affect their further protective ability. For that purpose, concentration of reactants (0.05–0.15 M Li2CO3), pH of the electrolyte (10–12), temperature (30–50 °C) and treatment time (15 min-30 h) were systematically varied. Additionally to that, NH4OH was applied as a chelating agent for the synthesis of Li-Al LDH-CO32-/OH– as well as for the pH control. The obtained protective coatings were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GDOES), Raman spectroscopy, salt spray test (SST) and electrochemical impedance spectroscopy (EIS). Among all varied parameters, involvement of chelating agent was found to be the most efficient for the formation of a coating with the highest level of corrosion protection. This is attributed to the formation of soluble complexes between NH4OH and Cu, resulting in dissolution of the intermetallics. It also prevents further redeposition of Cu species and consequently, the formation of new highly active Cu cathodes on the AA2024 alloy surface. %0 journal article %@ 2589-9651 %A Shulha, T.,Serdechnova, M.,Wu, T.,Naacke, T.,Wiese, G.,Blawert, C.,Zheludkevich, M.L. %D 2024 %J Nano Materials Science %N %P %R doi:10.1016/j.nanoms.2024.02.009 %T LDH sealing for PEO coated friction stir welded AZ31/AA5754 materials %U https://doi.org/10.1016/j.nanoms.2024.02.009 %X The need to combine various metals in light-weight constructions requires the development of coatings that prevent galvanic corrosion. Layered double hydroxides (LDHs) can be an example of such coatings, which were previously successfully obtained in situ on individual materials. In addition, the possibility of LDH growth (including LDH growth in the presence of chelating agents) on the surface of plasma electrolytic oxidation (PEO)-coated metals was previously shown. This PEO ​+ ​LDH combination could improve both corrosion and mechanical characteristics of the system. The possibility of LDHs formation in situ on the surface of PEO-coated friction stir welded (FSW) magnesium-aluminum materials (AZ31/AA5754 system was selected as a model one) was demonstrated in the presence of 1,3-diamino-2-hydroxypropane-N,N,N’,N’-tetraacetic acid (DHPTA) as a chelating agent, which was selected based on analysis of respective metal-ligand compounds stability. LDHs growth was achieved under ambient pressure without addition of carbonates in the electrolyte. The effectiveness of the resulting coating is shown both for corrosion resistance and hardness. %0 journal article %@ 0947-5117 %A Gazenbiller, E.,Arya, V.,Reitz, R.,Oechsner, M.,Zheludkevich, M.L.,Höche, D. %D 2024 %J Materials and Corrosion %N %P %R doi:10.1002/maco.202414388 %T Mechanistic insights into chemical corrosion kinetics of AA1050 in ethanol-blended fuels with water contamination via phase field modelling %U https://doi.org/10.1002/maco.202414388 %X Aluminum alloys are widely used in automotive construction, and since the introduction of biogenic ethanol into fuels, the issue of nonaqueous alcoholate corrosion has become an important topic. In this paper, the kinetics of AA1050 temperature-induced alcoholate pitting corrosion are examined experimentally with a specially constructed microreactor. The generated data are utilized to create a phase field model for the pit growth phase. The effects of ethanol-blend composition and water content are quantitatively assessed and simulated. Phase field simulations allow for the first time the mechanistic characterization of the chemical corrosion process with a water content of up to 0.3% and an estimation of relevant reaction parameters at temperatures of up to 150°C. The approach can further be utilized to develop strategies for minimizing corrosion risk in-service. %0 journal article %@ 0169-4332 %A Kong, W.,Serdechnova, M.,Kasneryk, V.,Gao, D.,Wang, H.,Xie, X.,Blawert, C.,Zheludkevich, M.L.,Zhang, Y. %D 2024 %J Applied Surface Science %N %P 130812 %R doi:10.1016/j.surfcoat.2024.130812 %T ZIF-8 based bifunctional coatings with anticorrosive and antibacterial properties: a new design strategy for more efficiency %U https://doi.org/10.1016/j.surfcoat.2024.130812 %X An efficient and simple in-situ/mechanical two-step strategy has been discovered for the fabrication of nanocontainers based on zeolite imidazole framework-8 (ZIF-8) with corrosion inhibitors (benzotriazole, BTA). The nanocontainers were applied in anticorrosive coatings with anticorrosion and antibacterial bifunctions for aluminum alloys AA2024. The effects of ZIF-8 modified with the corrosion inhibitor via different methods (in-situ, mechanical, and two-step strategies) on its morphology, composition, structure, loading/release behavior were studied and discussed. Results showed that the amount of loaded BTA was positively correlated with the crystal size of the final ZIF-8, impacting sustained release. Compared with the conventional primary load (in-situ and mechanical loading way), the two-step loading method (in-situ followed by mechanical treatment) achieved a higher BTA loading without evident ZIF-8 morphology and structure changes. The two-step modified (2-BTA@ZIF-8) powders exhibited good corrosion inhibition and remarkable antibacterial properties against Escherichia coli and Staphylococcus aureus. Additionally, the 1-BTA@ZIF-8 (in-situ strategy), 1-BTA/ZIF-8 (mechanical strategy) and 2-BTA@ZIF-8 composites were dispersed in acrylic resin to prepare anticorrosive and antibacterial bifunctional coatings. Results showed that the 2-BTA@ZIF-8 incorporated acrylic coatings exhibited superior anticorrosion performance and antimicrobial activity compared to the unmodified coating due to the controlled release of BTA. Thus, elaborated strategy represents a feasible and effective way to construct high-performance anticorrosive and antimicrobial coatings with metal-organic framework materials. %0 journal article %@ 1385-8947 %A Chen, Z.,Scharnagl, N.,Zheludkevich, M.,Ying, H.,Yang, W. %D 2023 %J Chemical Engineering Journal %N %P 138582 %R doi:10.1016/j.cej.2022.138582 %T Micro/nanocontainer-based intelligent coatings: Synthesis, performance and applications – A review %U https://doi.org/10.1016/j.cej.2022.138582 %X Metal corrosion causes huge economic losses, environmental pollution and industrial disasters. Application of smart self-healing coatings for the active corrosion protection of metal substrate has attracted substantial interest in recent years. The self-healing function can be achieved through either the intrinsic or extrinsic method. The intrinsic self-healing coatings mainly make use of the reversible physical and chemical interactions between molecules, whose self-healing effect is permanent. While the extrinsic method is mainly caused by embedding the micro/nanocontainers in the coatings, which can sense the micro-environmental changes and give rapid feedback to repair the micro cracked zones on the coating surface, the self-healing performance is temporary after the encapsulated active substances are fully consumed. Furthermore, inspired by these intelligent behaviors, more and more multi-functional coatings are designed and widely used in different fields. In this review, we summarized the research development of different stimuli-responsive self-healing coatings based on micro/nanocontainer techniques in recent years. Different types of micro/nanocontainers, as well as their synthesis or encapsulation technologies, are exampled to clarify the recent achievements. Meanwhile, the single stimulus-responsive systems are gradually evolved into the multi-stimulus-responsive system that endows the coatings with more sensitivity and intelligence. The stimuli-responsive self-healing coatings with different functions, such as self-reporting, anti-microbial, anti-fouling and self-lubrication functions, etc., are also explored, which enriches the application ranges of these smart coatings. This review investigated the research progress of the micro/nanocontainers-based self-healing coatings over the past few years and provided a unique insight into the future development of such smart coatings. %0 journal article %@ 1944-8244 %A Shulha, T.,Serdechnova, M.,Lamaka, S.V.,Lu, X.,Feiler, C.,Blawert, C.,Zheludkevich, M.L. %D 2023 %J ACS Applied Materials and Interfaces %N 4 %P 6098-6112 %R doi:10.1021/acsami.2c18675 %T Corrosion Inhibitors Intercalated into Layered Double Hydroxides Prepared In Situ on AZ91 Magnesium Alloys: Structure and Protection Ability %U https://doi.org/10.1021/acsami.2c18675 4 %X This work first describes the intercalation of corrosion inhibitors into layered double hydroxides LDH-OH/CO3 nanocontainers (parental LDH) obtained in situ on the surface of magnesium alloy AZ91 in the presence of a chelating agent. Vanadate, as a typical broad inhibitor for active metals, and oxalate, as an inhibitor suitable for magnesium, were selected as a first approach. The optimization of exchange conditions was performed, and the optimal parameters (ambient pressure and 95 °C) were selected. The corrosion protective properties of obtained LDH-based layers were studied using immersion and salt spray tests in NaCl solution, supported by electrochemical impedance spectroscopy and atomic emission spectroelectrochemistry. It is demonstrated that vanadate intercalated into LDH is more effective for the active protection of AZ91 in comparison to the performance of oxalate. A possible mechanism of corrosion inhibition based on the application of LDH nanocontainers is suggested and discussed. %0 journal article %@ 2213-9567 %A Wang, W.,Xu, W.,Höche, D.,Lamaka, S.,Zheludkevich, M. %D 2023 %J Journal of Magnesium and Alloys %N 1 %P 100-109 %R doi:10.1016/j.jma.2022.09.031 %T Exploring the contribution of oxygen reduction reaction to Mg corrosion by modeling assisted local analysis %U https://doi.org/10.1016/j.jma.2022.09.031 1 %X Oxygen reduction reaction (ORR) has been disclosed in recent studies as a significant secondary cathodic process during magnesium corrosion. This work elaborates on the contribution of ORR to the total corrosion process of pure Mg at different impurity levels in NaCl electrolyte with the assistance of local techniques. A finite element based numerical model taking into account the contribution of ORR during the corrosion of the Mg test materials has been designed in this study considering the local oxygen concentration. Respective computational simulations were calibrated based on the experimental data and evaluated accordingly. Finally, the simultaneous monitoring of local concentration of H2 and O2, and the combined modeling study reveal the relation between ORR and hydrogen evolution reaction. %0 journal article %@ 2213-9567 %A Zhang, G.,Wu, L.,Serdechnova, M.,Tang, A.,Wang, C.,Blawert, C.,Pan, F.,Zheludkevich, M. %D 2023 %J Journal of Magnesium and Alloys %N 7 %P 2376-2391 %R doi:10.1016/j.jma.2021.09.001 %T In-situ LDHs growth on PEO coatings on AZ31 magnesium alloy for active protection: Roles of PEO composition and conversion solution %U https://doi.org/10.1016/j.jma.2021.09.001 7 %X In this work, plasma electrolytic oxidation (PEO) coatings were produced on magnesium alloy AZ31 in aluminate, silicate and phosphate- based electrolytes, and followed by hydrothermal treatments in order to synthesis layered double hydroxides (LDHs) based nanocontainers. LDHs synthesis was done in three different growth solutions (deionized water, sodium nitrate and aluminum nitrate containing solution). In frame of this work it was shown, that it was difficult to form LDHs on Si-based PEO coating, due to more stable silicate phases in comparison with aluminate and phosphate phases in respective PEO coatings. The obtained hybrid LDH/PEO coatings were characterized using SEM, EDS and GDOES, and then the corrosion protection was further investigated by EIS. Based on the obtained results, it was confirmed that, the hydrothermal treatments in Al3+ %0 journal article %@ 2213-9567 %A Li, Y.,Lu, X.,Serdechnova, M.,Blawert, C.,Zheludkevich, M.L.,Qian, K.,Zhang, T.,Wang, F. %D 2023 %J Journal of Magnesium and Alloys %N 4 %P 1236-1246 %R doi:10.1016/j.jma.2021.07.015 %T Incorporation of LDH nanocontainers into plasma electrolytic oxidation coatings on Mg alloy %U https://doi.org/10.1016/j.jma.2021.07.015 4 %X In-situ incorporation of layered double hydroxides (LDH) nanocontainers into plasma electrolytic oxidation (PEO) coatings on AZ91 Mg alloy has been achieved in the present study. Fumarate was selected as Mg corrosion inhibitor for exchange and intercalation into the nanocontainers, which were subsequently incorporated into the coating. It was found that the thickness and compactness of the coatings were increased in the presence of LDH nanocontainers. The corrosion protection performance of the blank PEO, LDH containing PEO and inhibitor loaded coatings was evaluated by means of polarization test and electrochemical impedance spectroscopy (EIS). The degradation process and corrosion resistance of PEO coating were found to be greatly affected by the loaded inhibitor and nanocontainers by means of ion-exchange when corrosion occurs, leading to enhanced and stable corrosion resistance of the substrate. %0 journal article %@ 0169-1317 %A Kasneryk, V.,Serdechnova, M.,Blawert, C.,Zheludkevich, M.L. %D 2023 %J Applied Clay Science %N %P 106774 %R doi:10.1016/j.clay.2022.106774 %T LDH has been grown: What is next? Overview on methods of post-treatment of LDH conversion coatings %U https://doi.org/10.1016/j.clay.2022.106774 %X Current implementation of Industry 4.0, the fourth stage of industrialisation, implies application of novel approaches for manufacturing oriented on strong personalisation and customisation of products. In this context, formation of active multifunctional surfaces with on demand tailored properties can be considered as a keystone in the area of materials production. Nowadays, active multifunctional surfaces based on layered double hydroxides (LDH) are in the focus of numerous studies. Such interest is related to ability of LDH act as active “nanocontainers”, i.e. to intercalate and release active species in controllable manner. Formation of LDH-based materials with diverse physical-chemical properties for various applications can be achieved through their adjustable post-treatment. This review presents the actual state-of-the-art of LDH post-treatments, including methods preserving the LDH structures such as modifications with polymers, hydrophobic molecules and intercalation of functional species into their galleries; as well as approaches resulting in host LDH layers rearrangement like thermal treatment and recrystallization of layered double hydroxides to metal organic frameworks (LDH-to-MOF). %0 journal article %@ 1944-8244 %A Chen, Z.,Li, X.,Gong, B.,Scharnagl, N.,Zheludkevich, M.L.,Ying, H.,Yang, W. %D 2023 %J ACS Applied Materials and Interfaces %N 1 %P 2067-2076 %R doi:10.1021/acsami.2c17466 %T Double Stimuli-Responsive Conducting Polypyrrole Nanocapsules for Corrosion-Resistant Epoxy Coatings %U https://doi.org/10.1021/acsami.2c17466 1 %X Stimuli-responsive nanocapsules, which can respond to various environmental stimuli and release their encapsulated payload on demand, have attracted wide interest in different fields in recent years. In this work, a novel kind of polypyrrole (PPy) nanocapsules is fabricated and loaded with zinc salt corrosion inhibitors. The synthesized PPy nanocapsules respond to two different external stimuli (pH- and redox-responsive) and can control the release of their encapsulated corrosion inhibitors. The nanocapsules can detect the micro-environmental pH or surface-potential changes associated with the corrosion initiation of the metal substrate. When introduced into a protective epoxy coating, the fabricated PPy nanocapsules inhibit the anodic and cathodic corrosion reactions. The superior corrosion resistance and active corrosion protection effects of the epoxy-PPy-Zn coatings are further demonstrated via electrochemical and long-term immersion tests. The low-frequency impedance, coating resistance, and oxide film resistance increase after about 400 h of exposure in a 3.5 wt % NaCl solution, reflecting the enhanced corrosion protection properties and excellent repairing performance of the coating. Furthermore, the epoxy-PPy-Zn coating can avoid the pitting corrosion of 304 stainless steel. Overall, we have fabricated double stimuli-responsive PPy nanocapsules via a simple and effective strategy and incorporated them into a corrosion-resistant epoxy coating for protecting Fe-based metal substrates. %0 journal article %@ 2213-9567 %A Deng, M.,Wang, L.,Snihirova, D.,Bohlen, J.,Kurz, G.,Lamaka, S.V.,Höche, D.,Zheludkevich, M.L. %D 2023 %J Journal of Magnesium and Alloys %N 4 %P 1193-1205 %R doi:10.1016/j.jma.2022.12.014 %T Micro-alloyed Mg-Ca: Corrosion susceptibility to heating history and a plain problem-solving approach %U https://doi.org/10.1016/j.jma.2022.12.014 4 %X The exceptionally low corrosion rate (∼0.1 mm y–1 in concentrated NaCl solution for 7 days) enables lean Mg-Ca alloys great potential for diverse applications, particularly if relevant properties (e.g. mechanical strength, electrochemical performance, etc.) can be enhanced by thermomechanical processing. However, herein it is demonstrated that the corrosion performance of lean Mg-Ca is susceptible to the heating process. The corrosion rate of Mg-0.15 wt% Ca alloy is remarkably accelerated after annealing even for a short time (4 h at 400 °C) because Fe precipitation readily takes place. Fortunately, it is found that micro-alloying with dedicated additional elements is able to solve this problem. Nevertheless, the problem-solving capability is dependent on the element category, particularly the ability of the alloying element to constrain the Fe precipitation. Among the three studied elements (i.e. Sn, Ge and In), only In shows good competence of restricting the formation of Fe-containing precipitates, thereby contributing to retention of the superior corrosion resistance after annealing even at a rigorous condition (24 h at 450 °C). The finding creates good foundation for follow-up work of developing lean Mg-Ca-based alloys combining high corrosion resistance, superior electrochemical performance with excellent mechanical properties for applications as biodegradable implants and anode materials for aqueous batteries. %0 journal article %@ 0013-4686 %A Wang, L.,Snihirova, D.,Havigh, M.D.,Deng, M.,Lamaka, S.V.,Terryn, H.,Zheludkevich, M.L. %D 2023 %J Electrochimica Acta %N %P 143140 %R doi:10.1016/j.electacta.2023.143140 %T Non-stationarity in electrochemical impedance measurement of Mg-based materials in aqueous media %U https://doi.org/10.1016/j.electacta.2023.143140 %X For most bare Mg-based materials in aqueous media, an inductive behavior can be detected at the low frequencies electrochemical impedance spectroscopy (LF-EIS) measurement, which potentially can be associated with the non-stationarity of the system. The non-stationarity in EIS measurement leads to inaccurate acquisition of experimental data and, thus, misunderstanding of the electrochemical behavior of tested samples. To investigate the non-stationarity of EIS measurements on Mg-based materials in aqueous media, conventional EIS measurements are performed on pure Mg and several representative Mg alloys (AZ31, AZ91, AM50) in NaCl and Na2SO4 solutions. The results indicate that the impedance spectra of Mg-based materials in aqueous media is influenced by the internal non-stationarity of the Mg-electrolyte system and the external non-stationarity induced by EIS measurement. Multisine odd random phase EIS (ORP-EIS) measurements were performed to visualize the non-stationarity and non-linearity of the system. Moreover, the comparison of conventional and ORP-EIS results exhibits the difference between pseudo and real inductive behavior for the AZ31-NaCl system. Accordingly, the origin of the inductive behavior of Mg-based materials is discussed. %0 journal article %@ 0010-938X %A Wang, S.,Wang, Y.,Cao, G.,Chen, C.,Zhu, Y.,Serdechnova, M.,Blawert, C.,Zheludkevich, M.L..,Zou, Y.,Ouyang, J.,Jia, D.,Zhou, Y. %D 2023 %J Corrosion Science %N %P 111076 %R doi:10.1016/j.corsci.2023.111076 %T High temperature oxidation and hot corrosion behaviors of PEO and PEO/polysilazane preceramic-based dual-layer coatings on Ti6Al4V alloy %U https://doi.org/10.1016/j.corsci.2023.111076 %X The high temperature oxidation and corrosion behaviors of a plasma electrolytic oxidation (PEO) coating and a PEO/polysilazane (PEO/PSZ) dual-layer coating are investigated. After exposure in NaCl+Na2SO4 salt at 600 ℃ for 240 h, PEO coating tends to generate porous and loose scales, causing cracking or even complete peeling off from the substrate, and corrosion scales follow the law of formation-shedding-reformulation. After exposure in NaCl+Na2SO4 salt at 600 ℃ for 480 h, the PEO/PSZ coating exhibits a three-layer structure including the outermost corroded layer with sandwich structures, uncorroded Al2O3 particles-containing interlayer, and PEO bottom layer, which retards the continuous penetration of corrosive media and further diffusion of oxygen to the inner bulk alloy, resulting in a remarkable reduction of oxidation and corrosion rate. %0 journal article %@ 2397-2106 %A Li, X.,Vaghefinazari, B.,Würger, T.,Lamaka, S.V.,Zheludkevich, M.L.,Feiler, C. %D 2023 %J npj Materials Degradation %N %P 64 %R doi:10.1038/s41529-023-00384-z %T Predicting corrosion inhibition efficiencies of small organic molecules using data-driven techniques %U https://doi.org/10.1038/s41529-023-00384-z %X Selecting effective corrosion inhibitors from the vast chemical space is not a trivial task, as it is essentially infinite. Fortunately, machine learning techniques have shown great potential in generating shortlists of inhibitor candidates prior to large-scale experimental testing. In this work, we used the corrosion responses of 58 small organic molecules on the magnesium alloy AZ91 and utilized molecular descriptors derived from their geometry and density functional theory calculations to encode their molecular information. Statistical methods were applied to select the most relevant features to the target property for support vector regression and kernel ridge regression models, respectively, to predict the behavior of untested compounds. The performance of the two supervised learning approaches were compared and the robustness of the data-driven models were assessed by experimental blind testing. %0 journal article %@ 2397-2106 %A Schiessler, E.J.,Würger, T.,Vaghefinazari, B.,Lamaka, S.V.,Meißner, R.H.,Cyron, C.J.,Zheludkevich, M.L.,Feiler, C.,Aydin, R.C. %D 2023 %J npj Materials Degradation %N %P 74 %R doi:10.1038/s41529-023-00391-0 %T Searching the Chemical Space for Effective Magnesium Dissolution Modulators: A Deep Learning Approach using Sparse Features %U https://doi.org/10.1038/s41529-023-00391-0 %X Small organic molecules can alter the degradation rates of the magnesium alloy ZE41. However, identifying suitable candidate compounds from the vast chemical space requires sophisticated tools. The information contained in only a few molecular descriptors derived from recursive feature elimination was previously shown to hold the potential for determining such candidates using deep neural networks. We evaluate the capability of these networks to generalise by blind testing them on 15 randomly selected, completely unseen compounds. We find that their generalisation ability is still somewhat limited, most likely due to the relatively small amount of available training data. However, we demonstrate that our approach is scalable; meaning deficiencies caused by data limitations can presumably be overcome as the data availability increases. Finally, we illustrate the influence and importance of well-chosen descriptors towards the predictive power of deep neural networks. %0 journal article %@ 1611-3683 %A Ravikumar, A.,Höche, D.,Feiler, C.,Lekka, M.,Salicio-Paz, A.,Rohwerder, M.,Prabhakar, M.J,Zheludkevich, M.L. %D 2023 %J Steel Research International %N %P 2300353 %R doi:10.1002/srin.202300353 %T Exploring the effect of microstructure and surface recombination on hydrogen effusion in Zn-Ni coated martensitic steels by advanced computational modeling %U https://doi.org/10.1002/srin.202300353 %X Ultrahigh-strength steel (UHSS) structures are plated with Zn–Ni coatings because of their excellent corrosion resistance properties, but the plating process is accompanied by the production of hydrogen. The presence of hydrogen in steel results in hydrogen embrittlement. Hence, during the production of UHSS parts, dedicated outgassing steps are employed to remove the diffusible hydrogen from the steel. In a production environment, the real effect of the outgassing process and the outgassing efficiency is unknown for parts coated with Zn–Ni. Hence, a finite element model is developed to capture the evolution of the hydrogen concentration profile in coated UHSS parts during outgassing to study the influence of coating morphology and microstructural features of steel. In order to develop the geometry of the model, scanning electron microscope images are analyzed to understand the microstructure and morphology of the coating. Numerical samples are generated by combining different coating morphologies with steel substrates of varying microstructural features to attain a series of samples with varying features. The results of the outgassing simulations clearly demonstrate the major role of the coating morphology on the hydrogen flux. %0 journal article %@ 0010-938X %A Wei, K.,Wei, Y.,Zhang, Y.,Kasneryk, V.,Serdechnova, M.,Wang, H.,Zhang, Z.,Yuan, Y.,Blawert, C.,Zheludkevich, M.L.,Chen, F. %D 2023 %J Corrosion Science %N %P 111731 %R doi:10.1016/j.corsci.2023.111731 %T In Situ Synthesis of ZIF-8 Loaded with 8-hydroxyquinoline Composite via a Host-Guest Nanoconfinement Strategy for High-Performance Corrosion Protection %U https://doi.org/10.1016/j.corsci.2023.111731 %X A strategy based on in situ host-guest nanoconfinement was used to assist the synthesis of a ZIF-8 host loaded with a corrosion inhibitor 8-hydroxyquinoline (8-HQ) guest by a facile one-step process at room temperature. Results showed that a Zn-(bis-8-hydroxyquinoline) guest encapsulated ZIF-8 host composite (Q@ZIF-8) was formed. The Q@ZIF-8 proves to have an inhibition efficiency of over 91% to protect the aluminum alloy substrate against corrosion in the corrosive solution after 2 days. Additionally, the pH-responsive Q@ZIF-8 can release 8-HQ species in form of hydroxyquinoline zinc complex and improves the corrosion resistance of the epoxy coating. %0 journal article %@ 2079-4983 %A Moreno, L.,Wang, C.,Lamaka, S.V.,Zheludkevich, M.L.,Rodríguez-Hernández, J.,Arrabal, R.,Matykina, E. %D 2023 %J Journal of Functional Biomaterials %N 2 %P 65 %R doi:10.3390/jfb14020065 %T Ciprofloxacin Release and Corrosion Behaviour of a Hybrid PEO/PCL Coating on Mg3Zn0.4Ca Alloy %U https://doi.org/10.3390/jfb14020065 2 %X In the present work, a hybrid hierarchical coating (HHC) system comprising a plasma electrolytic oxidation (PEO) coating and a homogeneously porous structured polycaprolactone (PCL) top-coat layer, loaded with ciprofloxacin (CIP), was developed on Mg3Zn0.4Ca alloy. According to the findings, the HHC system avoided burst release and ensured gradual drug elution (64% over 240 h). The multi-level protection of the magnesium alloy is achieved through sealing of the PEO coating pores by the polymer layer and the inhibiting effect of CIP (up to 74%). The corrosion inhibition effect of HHC and the eluted drug is associated with the formation of insoluble CIP-Me (Mg/Ca) chelates that repair the defects in the HHC and impede the access of corrosive species as corroborated by FTIR spectra, EIS and SEM images after 24 h of immersion. Therefore, CIP participates in an active protection mechanism by interacting with cations coming through the damaged coating. %0 journal article %@ 2213-9567 %A Chen, Y.,Wu, L.,Yao, W.,Wu, J.,Serdechnova, M.,Blawert, C.,Zheludkevich, M.L.,Yuan, Y.,Pan, F. %D 2023 %J Journal of Magnesium and Alloys %N 7 %P 2230-2259 %R doi:10.1016/j.jma.2023.06.006 %T "Smart" micro/nano container-based self-healing coatings on magnesium alloys: A review %U https://doi.org/10.1016/j.jma.2023.06.006 7 %X Coating technologies are a commonly used way to protect metals against corrosion. However, with more and more severe service environments of materials, many protective coating systems often are not environmentally friendly or toxic as in the case of chromates. Based on the world's abundant ideal magnesium (Mg) and its alloy, the smart self-healing anticorrosive coating can autonomously restore the damaged part of the coating according to the environmental changes, strengthen the corrosion protection ability, and prolong its service life. This paper reviews the research progress of smart self-healing coatings on Mg alloys. These coatings mostly contain suitable corrosion inhibitors encapsulated into micro/nano containers. Moreover, the different self-healing mechanisms and functionalities of micro/nano containers are discussed. The micro/nano containers range from inorganic nanocontainers such as mesoporous nanoparticles (silica (SiO2), titanium dioxide (TiO2), etc.), over inorganic clays (halloysite, hydrotalcite-like, zeolite), to organic nanocontainers such as polymer microcapsules, nanofibers, chitosan (CS) and cyclodextrin (CD), as well as, carbon materials such as graphene and carbon nanotubes and hybrids such as metal organic frameworks. The functioning of micro/nano containers can be divided in two principal groups: autonomous (based on defect filling and corrosion inhibition) and non-autonomous (based on dynamic bonds and shape memory polymers). Moreover, multi functionalities and composite applications of various micro/nano containers are summarized. At present, significant progress has been made in the preparation methods and technologies of micro/nano containers. Achieving long-term self-healing properties of coatings sensing of coating failure and early warning after self-healing function failure can be expected as the main development direction of self-healing corrosion protection coatings in the future. %0 journal article %@ 0010-938X %A Wang, C.,Song, C.,Mei, D.,Wang, L.,Wang, W.,Wu, T.,Snihirova, D.,Zheludkevich, M.,Lamaka, S. %D 2022 %J Corrosion Science %N %P 110059 %R doi:10.1016/j.corsci.2021.110059 %T Low interfacial pH discloses the favorable biodegradability of several Mg alloys %U https://doi.org/10.1016/j.corsci.2021.110059 %X Low interfacial pH (7.5–8.0) and corrosion rate were found for several Mg alloys (CP-Mg, UHP-Mg, Mg-0.15 wt%Ca, Mg-4 wt%Ag) in Ca2+-containing Hanks’ Balanced Salt Solution (HBSS, = 7.4) at 37 °C under hydrodynamic condition. Low interfacial pH and corrosion rate originated from the facilitated formation of the protective calcium-phosphate-rich precipitates at 37 °C. This study indicates that Mg degradation in a quasi-physiological environment causes only slight alkalization (pH < 8.0), as opposed to the high local and bulk pH (ca. 10.4) characteristic for Mg in NaCl electrolyte. It is also stressed that no synthetic pH buffers should be added to constantly supplied Ca2+-containing HBSS. %0 journal article %@ 0378-7753 %A Vaghefinazari, B.,Snihirova, D.,Wang, C.,Wang, L.,Deng, M.,Höche, D.,Lamaka, S.V.,Zheludkevich, M.L. %D 2022 %J Journal of Power Sources %N %P 231176 %R doi:10.1016/j.jpowsour.2022.231176 %T Exploring the effect of sodium salt of Ethylenediaminetetraacetic acid as an electrolyte additive on electrochemical behavior of a commercially pure Mg in primary Mg-air batteries %U https://doi.org/10.1016/j.jpowsour.2022.231176 %X In this study, sodium salt of Ethylendiaminetetraacetic acid (EDTA), a strong and widely-used complexing agent, was utilized as an additive for a primary Mg-air battery electrolyte with a commercially pure magnesium anode. The electrolyte pH (ranged 7.0 to 11.0) was taken as the main parameter to explore the effect of EDTA on the discharge performance of the Mg anode. The results show that the most negative half-cell discharge potential of the Mg anode is achieved in the slightly alkaline pH around 9, at which the EDTA has the strongest ability to prevent the formation of fouling Mg(OH)2 and improve the anode activity. The utilization efficiency of the discharged Mg anode is enhanced with the increase in pH of the electrolyte due to several mechanisms, including suppressing the chunk effect, weakening the detrimental Negative Difference Effect (NDE), and promoting the formation of a more protective layer on the Mg anode surface. %0 journal article %@ 1005-0302 %A Yao, W.,Wu, L.,Wang, J.,Jiang, B.,Zhang, D.,Serdechnova, M.,Shulha, T.,Blawert, C.,Zheludkevich, M.,Pan, F. %D 2022 %J Journal of Materials Science & Technology %N %P 158-180 %R doi:10.1016/j.jmst.2021.11.053 %T Micro‐arc oxidation of magnesium alloys: A review %U https://doi.org/10.1016/j.jmst.2021.11.053 %X Magnesium (Mg) and its alloys present great potential to be extensively applied in different applications. However, the relatively poor resistance to corrosion and wear significantly restricts their applications in practice. As one of strategies of surface treatment, micro-arc oxidation (MAO) process attracts a lot of attention, since it does not use neither expensive equipment, nor complicated manipulation. This review systematically discusses MAO mechanism and some typical models, which still need to be further developed to provide a better understanding and guide for future researchers. Subsequently, main influencing factors of MAO process are analyzed in detail. Further, some popular applications of MAO coatings are respectively reviewed, including biomedical application, decoration, thermal control, corrosion and wear resistance, and industrial applications in practice. The existing issues and future perspectives are finally discussed to further accelerate extensive applications of Mg alloys. %0 journal article %@ 1875-5100 %A Ben Seghier, M.,Höche, D.,Zheludkevich, M. %D 2022 %J Journal of Natural Gas Science and Engineering %N %P 50288 %R doi:10.1016/j.jngse.2022.104425 %T Prediction of the internal corrosion rate for oil and gas pipeline: Implementation of ensemble learning techniques %U https://doi.org/10.1016/j.jngse.2022.104425 %X This paper proposes a practical implementation of robust ensemble learning models for accurate prediction of the internal corrosion rate in oil and gas pipelines. A correct assessment of the corrosion rate in fluid flowed oil and gas pipelines has a significant influence on the system's safety and the ability to control operation. The developed predictive data driven models include four ensemble learning approaches, namely random forest, adoptive boosting, gradient boosting regression tree, and extreme gradient boosting. The implementation procedure of these predictive models integrates a comprehensive database of eight system descriptors, extracted from the literature, while k-fold cross validation is employed to guarantee high performance and generalization. In addition, the obtained results of the internal corrosion rate are subjected to rigorous statistical and graphical analysis to evaluate the models performance and compare their abilities. The extreme gradient boosting model indicate the highest performance in the prediction of the internal corrosion rate in oil and gas pipelines based on the calculated single and global metrics, with a mathematical RMSE value of internal corrosion rate 0.031 mm/y and performance index, PI = 0.61. Besides, the significance of the input variables is determined through a sensitivity analyses by using feature importance criteria, whereas for the applied dataset strongest corrosion rate dependency to temperature and the pressure was shown beside the CO2 contribution. In overall, the ensemble learning models show a significant performance in the internal corrosion rate predictions, while the extreme gradient boosting model is beneficial to model the internal corrosion rate in oil and gas pipelines due to its high performance. %0 journal article %@ 0257-8972 %A Han, J.,Yu, Y.,Yang, J.,Xiaopeng, L.,Blawert, C.,Zheludkevich, M.L. %D 2022 %J Surface and Coatings Technology %N %P 128112 %R doi:10.1016/j.surfcoat.2022.128112 %T Corrosion and wear performance of La2O3 doped plasma electrolytic oxidation coating on pure Mg %U https://doi.org/10.1016/j.surfcoat.2022.128112 %X With the aim of improving the corrosion and wear resistance of pure magnesium, La2O3 nano-particles are added into the PEO electrolyte. The influence of the particles on coating formation, morphology and performance is investigated. Results indicate that the porosity and thickness decrease remarkably after the particle incorporation which influences the corrosion and wear resistance in return. The coating with 1 g particle addition shows lowest porosity and highest hardness value, resulting in superior corrosion and wear performance, which implies the feasibility of the proposed strategy in fabricating functionalized PEO coatings on Mg-based materials. %0 journal article %@ 2213-9567 %A Wu, T.,Blawert, C.,Serdechnova, M.,Karlova, P.,Dovzhenko, G.,Wieland, F.,Zheludkevich, M. %D 2022 %J Journal of Magnesium and Alloys %N 2 %P 423-439 %R doi:10.1016/j.jma.2021.09.017 %T PEO processing of AZ91Nd/Al2O3 MMC-the role of alumina fibers %U https://doi.org/10.1016/j.jma.2021.09.017 2 %X This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC (metal matrix composite) on the PEO coating formation process in a sodium phosphate-based electrolyte. By comparison with the pure AZ91Nd, the evolution of alumina fiber during the processing and the characteristics of the resultant PEO coating were investigated. The voltage response as a function of processing time was changed. Lower voltage in the presence of alumina fiber is responsible for the lower coating thickness. The morphology and phase composition of the coatings are also influenced by the incorporation of the fiber. Firstly, the fiber is embedded in the coating and interrupts the continuity of the coating. With increasing processing time, the fiber is found to be reactively incorporated in the coating. The intention to produce a MgAl2O4 containing coating is achieved and it is mainly accumulated near the coating surface. However, due to the low number of fibers, the Al content is overall still low and only near to the fibers the MgAl2O4 spinel phase can form. %0 journal article %@ 0010-938X %A Wang, C.,Liu, X.,Mei, D.,Deng, M.,Zheng, Y.,Zheludkevich, M.,Lamaka, S. %D 2022 %J Corrosion Science %N %P 110061 %R doi:10.1016/j.corsci.2021.110061 %T Local pH and oxygen concentration at the interface of Zn alloys in Tris-HCl or HEPES buffered Hanks’ balanced salt solution %U https://doi.org/10.1016/j.corsci.2021.110061 %X Although Tris-HCl and HEPES are typically used pH buffers for in vitro studies, they are recently proven to be unable to stabilize local pH at Mg interface in simulated body fluids. In this study, local pH close to physiological (7.1–7.5) was found at metal/fluid interface of pure Zn, Zn-0.8 wt%Ca and Zn-0.8 wt%Mg alloys in Tris-HCl or HEPES buffered Hanks’ balanced salt solution (HBSS) at 37 °C under hydrodynamic conditions. High rate oxygen consumption was detected above Zn alloys in various HBSS electrolytes. These findings support the previous recommendation of using synthetic pH buffers for in vitro studies of biodegradable Zn-based alloys. %0 journal article %@ 0010-938X %A Yasakau, K.,Maltseva, A.,Lamaka, S.,Mei, D.,Ovri, H.,Volovitch, P.,Ferreira, M.,Zheludkevich, M. %D 2022 %J Corrosion Science %N %P 109937 %R doi:10.1016/j.corsci.2021.109937 %T The effect of carboxylate compounds on Volta potential and corrosion inhibition of Mg containing different levels of iron %U https://doi.org/10.1016/j.corsci.2021.109937 %X Corrosion protection and surface properties of Magnesium (Mg) containing 51 ppm Fe (HP-Mg) and 341 ppm Fe (CP-Mg) were assessed by EIS, AFM/SKPFM, and photoluminescence spectroscopy in NaCl solutions with/without fumarate (Fum), 2,5-pyridinedicarboxylate (PDCA) and salicylate (Sal) carboxylates. The PDCA was effective in corrosion inhibition of HP-Mg and CP-Mg, while the Sal was efficient in inhibition of CP-Mg only. Volta potential (VPD) changes on Mg were evaluated considering the contribution of molecular dipoles and chemical dipoles due to interaction of carboxylate groups present in carboxylates with Mg. VPD of CP-Mg increased due to adsorption of Fe(III)-salicylate complexes and salicylate molecules. %0 journal article %@ 0257-8972 %A Rakoch, A.G.,Van Tuan, T.,Khabibullina, Z.V.,Blawert, C.,Serdechnova, M.,Scharnagl, N.,Zheludkevich, M.L.,Gladkova, A.A. %D 2022 %J Surface and Coatings Technology %N %P 128075 %R doi:10.1016/j.surfcoat.2021.128075 %T Role of cobalt additive on formation and anticorrosion properties of PEO coatings on AA2024 alloy in alkali-silicate electrolyte %U https://doi.org/10.1016/j.surfcoat.2021.128075 %X Mechanisms of PEO coatings formation on AA2024 aluminum alloy in an aqueous solution, containing 3 g/L NaOH and 5 g/L Na2O∙2.9SiO2∙18H2O (base electrolyte) and with addition of 1.5 g/L CoOOH∙H2O, are studied. This addition results in a formation of black coatings. It is determined that structure, phase and elemental compositions of the coatings correlated with the corrosion properties. For coatings, grown in the base electrolyte, anodic and cathodic current densities and the value of impedance modulus (|Z|f=0.01Hz) improves with the increase of the coatings thickness due to the healing of internal pores during extended PEO processing, according to the results of electrochemical measurements in 0.5 wt% NaCl solution. However, the results of electrochemical tests of coatings, synthesized in the electrolyte with CoOOH∙H2O differ. For short-term immersion (up to 24 h), thin coating (~17 μm) demonstrates the lowest current densities and the highest value of impedance modulus (|Z|f=0.01Hz) in comparison to the thicker coatings (~48, 82 μm). However, after longer exposure (up to 168 h) the thickest coating (~82 μm) has the best long-term stability. This behavior and the most probable mechanism of black coatings formation are suggested and explained as function of coating properties and exposure time in NaCl solution. %0 journal article %@ 2213-9567 %A Shulha, T.,Serdechnova, M.,Iuzviuk, M.,Zobkalo, I.,Karlova, P.,Scharnagl, N.,Wieland, F.,Lamaka, S.,Yaremchenko, A.,Blawert, C.,Zheludkevich, M. %D 2022 %J Journal of Magnesium and Alloys %N 5 %P 1268-1285 %R doi:10.1016/j.jma.2021.10.006 %T In situ formation of LDH-based nanocontainers on the surface of AZ91 magnesium alloy and detailed investigation of their crystal structure %U https://doi.org/10.1016/j.jma.2021.10.006 5 %X In the presented work, the possibility of direct synthesis of LDH (layered double hydroxide) on the AZ91 surface in the presence of a chelating agent (diethylenetriaminepentaacetic acid - DTPA) is reported. Conversion layer of LDH nanocontainers were formed under ambient pressure conditions without carbonate addition in the electrolyte. The obtained LDH was characterized using experimental (SEM, XRD, TGA, XPS, Raman, etc.) and computational methods (thermodynamic calculation, modeling of possible LDH crystal structures). A comparison of three possible LDHs (LDH-OH, -NO3 and -CO3) was performed. Based on the experimental results and crystal simulation approach, it was confirmed, that the mixed LDH-OH/CO3 is grown on the surface in the presence of DTPA pentasodium salt. %0 journal article %@ 0143-7496 %A Gazenbiller, E.,Khan, Q.A.,Rico-Oller, B.,Hackner, A.,Meer, T.,Hack, T.,Langer, B.,Beneke, M.,Kröger-Kallis, B.,Zheludkevich, M.L.,Höche, D. %D 2022 %J International Journal of Adhesion and Adhesives %N %P 103049 %R doi:10.1016/j.ijadhadh.2021.103049 %T Semiconducting properties of surface-treated titanium and their effect on peel resistance: Experimental and modelling studies %U https://doi.org/10.1016/j.ijadhadh.2021.103049 %X Adhesively-bonded titanium components enable new design concepts in lightweight engineering but often lack long-term joint durability and endurance. Major challenges are related to the fact that the titanium/adhesive interface is susceptible to environmental ageing which leads to interfacial deadhesion. In the present work, the issue is addressed from the standpoint of semiconducting properties of surface TiO2 films. Examination of surface treated, anodized cp-Ti has been conducted using electrochemical impedance spectroscopy (EIS). Semiconducting properties of titanium oxide films were derived from Mott-Schottky analysis whereas roller-peel tests were considered for joint strength assessment before and after accelerated ageing in climate chambers. The experimental study is complemented by a computational study on the adhesion force distribution during roller peel testing based on a cohesive zone FEM model.,The studies show clear indication for a complex interaction between the adhesion contributing underlying physio-chemical mechanisms. Crucial insights into the electrochemistry at the respective interfaces and their relevance for joint design are provided. %0 journal article %@ 0013-4686 %A Wang, L.,Snihirova, D.,Deng, M.,Vaghefinazari, B.,Höche, D.,Lamaka, S.,Zheludkevich, M. %D 2022 %J Electrochimica Acta %N %P 139582 %R doi:10.1016/j.electacta.2021.139582 %T Revealing physical interpretation of time constants in electrochemical impedance spectra of Mg via Tribo-EIS measurements %U https://doi.org/10.1016/j.electacta.2021.139582 %X Tribo-electrochemical impedance spectroscopy (Tribo-EIS) measurements of pure Mg were performed to identify the origin of two time constants during standard EIS measurements in NaCl solution. The influence of abrasion introduced by tribometer on EIS spectra was investigated under different rotation speeds. Further quantitative analyses of abrasion on Mg with different surface areas were performed. The resistances associated to the two time constants on the abraded surface were deduced from the fitted results, verifying that the high frequency time constant originates from the barrier properties of the MgO-based surface film and the middle frequency time constant stems from the charge transfer process. %0 journal article %@ 0169-4332 %A Wu, T.,Blawert, C.,Serdechnova, M.,Karlova, P.,Dovzhenko, G.,Wieland, F.,Stojadinovic, S.,Vasilicd, R.,Mojsilovic, K.,Zheludkevich, M. %D 2022 %J Applied Surface Science %N %P 151629 %R doi:10.1016/j.apsusc.2021.151629 %T Formation of plasma electrolytic oxidation coatings on pure niobium in different electrolytes %U https://doi.org/10.1016/j.apsusc.2021.151629 %X The development of PEO surface treatments for Nb (niobium) provides a possibility to produce functionalized coatings with a combination of new compositions and phases. In the frame of this work, PEO coatings on pure Nb are produced in three electrolytes containing aluminate, phosphate and silicate. Furthermore, the influence of the electrolyte composition on the PEO process and the microstructure, composition and properties of the coatings were studied. It was observed that most of the coating forming species did not participate in the plasma reactions directly, while the chemical-, electrochemical- and thermal stimulated reactions are dominating the coating formation. The results show that all the coatings are mainly composed of the Nb2O5 phase. An additional mixture of oxides (Al2O3 and AlNbO4) is found in the coating formed in aluminate-containing electrolyte, and the coating formed in phosphate-containing electrolyte contains a small amount of Nb2(PO4)3 and amorphous phosphate. No additional crystalline phase other than the amorphous silica phase is detected in the coating formed in silicate-containing electrolyte. Additionally, different morphology of the coatings is revealed and the most uniform coating is produced in silicate-containing electrolyte, which further improves its corrosion resistance. This coating also shows the highest photocatalytic activity due to the combination of Nb2O5 and silica. Since all PEO coatings on pure Nb show superior corrosion resistance and photocatalytic activity, they might be interesting for a wide range of applications ranging from transportation, biomedical implants to environmental protection. %0 journal article %@ 1385-8947 %A Wang, L.,Snihirova, D.,Deng, M.,Vaghefinazari, B.,Höche, D.,Lamaka, S.,Zheludkevich, M. %D 2022 %J Chemical Engineering Journal %N %P 132369 %R doi:10.1016/j.cej.2021.132369 %T Enhancement of discharge performance for aqueous Mg-air batteries in 2;6-dihydroxybenzoate-containing electrolyte %U https://doi.org/10.1016/j.cej.2021.132369 %X In this work, 2,6-dihydroxytbenzoate (2,6-DHB) is evaluated as an efficient electrolyte additive for aqueous Mg-air batteries based on diverse metallic Mg anodes. EIS measurements amid intermittent discharge and real-time hydrogen evolution measurements during discharge were applied to clarify the effective mechanism. The dependence of working mechanism on 2,6-DHB concentration was investigated for a newly developed Mg-0.15Ca anode. The results reveal that sufficient amount of 2,6-DHB simultaneously improves the discharge activity and inhibits the self-discharge of Mg-0.15Ca anode, leading to negative average potential and high anodic utilization efficiency. Accordingly, 0.2 M 2,6-DHB is determined as the most suitable electrolyte concentration and applied during Mg-air battery tests based on diverse commercial Mg anodes (pure Mg, Mg-0.15Ca, AZ31 and AM50). The results demonstrate that 2,6-DHB efficiently improves the discharge performance of Mg-air batteries with different Mg anodes. %0 journal article %@ 2452-199X %A Wang, C.,Tonna, C.,Mei, D.,Buhagiar, J.,Zheludkevich, M.,Lamaka, S. %D 2022 %J Bioactive Materials %N %P 412-425 %R doi:10.1016/j.bioactmat.2021.05.014 %T Biodegradation behaviour of Fe-based alloys in Hanks’ Balanced Salt Solutions: Part II. The evolution of local pH and dissolved oxygen concentration at metal interface %U https://doi.org/10.1016/j.bioactmat.2021.05.014 %X Commercially pure Fe, Fe35Mn, and (Fe35Mn)5Ag alloys were prepared by uniaxial pressing of the mixture of individual powders, followed by sintering. The influence of the alloying elements Mn and Ag on the corrosion behaviour of these Fe-based alloys was investigated in Hanks’ Balanced Salt Solution (HBSS). Furthermore, the role of the components in HBSS, particularly Ca2+ ions during alloys degradation was studied. Distribution of local pH and dissolved oxygen concentration was measured 50 μm above the interface of the degrading alloys. The results revealed that 5 wt% Ag addition to Fe35Mn alloy triggered micro-galvanic corrosion, while uniform corrosion dominated in pure Fe and Fe35Mn. Fast precipitation of Ca–P-containing products on the surface of these Fe-based alloys buffered local pH at the metal interface, and blocked oxygen diffusion at the initial stages of immersion. In the (Fe35Mn)5Ag, the detachment or structural changes of Ca–P-containing products gradually diminished their barrier property. These findings provided valuable insights into the degradation mechanism of promising biodegradable Fe-based alloys. %0 journal article %@ 2470-1343 %A Li, X.,Würger, T.,Feiler, C.,Meißner, R.,Serdechnova, M.,Blawert, C.,Zheludkevich, M. %D 2022 %J ACS Omega %N 14 %P 12412-12423 %R doi:10.1021/acsomega.2c01115 %T Atomistic Insight into the Hydration States of Layered Double Hydroxides %U https://doi.org/10.1021/acsomega.2c01115 14 %X Effective protective coatings are an essential component of lightweight engineering materials in a large variety of applications as they ensure structural integrity of the base material throughout its whole service life. Layered double hydroxides (LDHs) loaded with corrosion inhibitors depict a promising approach to realize an active corrosion protection for aluminum and magnesium. In this work, we employed a combination of density functional theory and molecular dynamics simulations to gain a deeper understanding of the influence of intercalated water content on the structure, the stability, and the anion-exchange capacity of four different LDH systems containing either nitrate, carbonate, or oxalate as potential corrosion inhibiting agents or chloride as a corrosion initiator. To quantify the structural change, we studied the atom density distribution, radial distribution function, and orientation of the intercalated anions. Additionally, we determined the stability of the LDH systems by calculating their respective hydration energies, hydrogen-bonded network connected to the intercalated water molecules, as well as the self-diffusion coefficients of the intercalated anions to provide an estimate for the probability of their release after intercalation. The obtained computational results suggest that the hydration state of LDHs has a significant effect on their key properties like interlayer spacing and self-diffusion coefficients of the intercalated anions. Furthermore, we conclude from our simulation results that a high self-diffusion coefficient which is linked to the mobility of the intercalated anions is vital for its release via an anion-exchange mechanism and to subsequently mitigate corrosion reactions. Furthermore, the presented theoretical study provides a robust force field for the computer-assisted design of further LDH-based active anticorrosion coatings. %0 journal article %@ 2095-8226 %A Zhu, Y.,Song, G.,Zheng, D.,Serdechnova, M.,Blawert, C.,Zheludkevich, M. %D 2022 %J Science China Materials %N 7 %P 1842-1852 %R doi:10.1007/s40843-021-1975-y %T In situ synergistic strategy of sacrificial intermedium for scalable-manufactured and controllable layered double hydroxide film %U https://doi.org/10.1007/s40843-021-1975-y 7 %X Layered double hydroxides (LDHs), a class of two-dimensional (2D) brucite-like layers, have been effectively applied in diverse fields. However, the current synthesis methods restrict the in situ scaling-up and tunable production of LDH-based materials. Inspired by the growing characteristic of “Bryophyllum pinnatum”, a sacrificial co-sputtered Zn−Al transition layer was introduced for the first time to in situ grow a scalable-manufactured and thickness-controllable LDH film on arbitrary substrate materials with flexible shapes through “partial dissolution” and “solution infiltration” processes. Diverse LDH films could be tailored by the creative regulation of the component, structure and surface state of the transition layer. Results showed that the as-prepared LDH film had strong mechanical robustness under harsh abrasion conditions due to its large thickness and multi-level microstructure. Moreover, a series of galvanic couple model experiments based on Zn/Al single-metal transition layers were designed to solve the real-time monitoring issue in the complex hydrothermal solution. This work not only develops a new strategy to design and grow in situ LDH films with multifaceted features, but also reveals sophisticated LDH formation mechanisms. Hence, the findings of this study may broaden the practical application of LDH-based materials toward advanced and smart devices. %0 journal article %@ 1996-1944 %A Campos, M.,Blawert, C.,Scharnagl, N.,Störmer, M.,Zheludkevich, M. %D 2022 %J Materials %N 4 %P 1301 %R doi:10.3390/ma15041301 %T Cathodic Protection of Mild Steel Using Aluminium-Based Alloys %U https://doi.org/10.3390/ma15041301 4 %X Typically, steel is protected from corrosion by employing sacrificial anodes or coatings based on Zn, Mg, Al or Cd. However, stricter environmental regulations require new environmentally friendly alternatives to replace Cd. Traditionally, Al-based anodes have been employed to cathodically protect steel in marine applications or as ion vapour deposition (IVD)-Al sacrificial coatings for aerospace applications. However, Al tends to passivate, thus losing its protective effect. Therefore, it is important to identify possible alloys that can provide a constantly sufficient current. In this study, Al-X alloys (X = Ag, Bi, Ca, Cr, Cu, Ga, Gd, In, Mg, Mn, Ni, Sb, Si, Sn, V, Ti, Zn and Zr) were firstly tested for a screening of the sacrificial properties of binary systems. Al-0.5Cr, Al-1Sn, Al-0.2Ga, Al-0.1In, Al-2Si and Al-5Zn alloys were suggested as promising sacrificial Al-based alloys. Suitable heat treatments for each system were implemented to reduce the influence of the secondary phases on the corrosion properties by minimising localised attack. extensive evaluation of the corrosion properties, including galvanic coupling of these alloys to steel, was performed in the NaCl electrolyte. A comparative analysis was conducted in order to choose the most promising alloy(s) for avoiding the passivation of Al and for efficient cathodic protection to steel. %0 journal article %@ 0257-8972 %A Dou, Z.,Zhang, Y.,Shulha, T.,Cui, R.,Serdechnova, M.,Tian, H.,Yan, T.,Blawert, C.,Li, L.,Zheludkevich, M.L.,Chen, F. %D 2022 %J Surface and Coatings Technology %N %P 128414 %R doi:10.1016/j.surfcoat.2022.128414 %T Insight into chelating agent stimulated in-situ growth of MgAl-LDH films on magnesium alloy AZ31: The effect of initial cationic concentrations %U https://doi.org/10.1016/j.surfcoat.2022.128414 %X A strategy based on chelating agent addition was used to assist the in-situ growth of MgAl-layered double hydroxides (LDHs) films on magnesium alloy AZ31 in a relatively mild condition. The growth behavior of MgAl-LDH films was studied on the magnesium alloy AZ31 substrate as the sole source of Al3+ and/or adding aluminum compounds as a supplementary source of respective ions. The composition, structure, corrosion resistance, and formation mechanism of LDH films were investigated and discussed. Results showed that the LDH-coated samples could effectively retard the corrosion of magnesium alloy. A thicker Mg (OH)2/MgAl-LDH composite film with larger flake size was formed without additional aluminum source. MgAl-LDH film fabricated with moderate additional Al3+ concentrations showed better corrosion resistance and an interesting stable network structure on a flat surface both covered/consisting of very fine LDH flakes. %0 journal article %@ 0257-8972 %A Gazenbiller, E.,Mansoor, S.,Konchakova, N.,Serdechnova, M.,Zheludkevich, M.L.,Blawert, C.,Höche, D. %D 2022 %J Surface and Coatings Technology %N %P 128758 %R doi:10.1016/j.surfcoat.2022.128758 %T Computational damage modelling of PEO coated extruded magnesium tested in slow strain rate configuration %U https://doi.org/10.1016/j.surfcoat.2022.128758 %X Mechanical damage induced failure within protective coatings is one of the main reasons for loss of coating integrity. Thus, for applicability of any coating and sealing technology it is mandatory to know the stress/strain levels at which mechanical component failure will occur and it is important to understand which physical entities drive damage initiation and propagation. Within this work a model has been developed which allows correlating and study the effect of brittle porous coatings on the stress-strain curve evolution of plasma electrolytic oxidation (PEO) coated extruded Mg substrates. This is a great benefit as deriving material laws might be challenging since measured stress-strain relationships are a convolution of substrate and coating material contribution. The approach is based on a damage model which allows distinguishing between the substrate contribution model as a bulk body described by dedicated material laws, and the brittle coating contribution mathematically modelled as a boundary condition. The effect of coating thickness, the resulting steady state crack spacing and the contribution of coating porosity on the stress-strain curve is shown. The approach allows direct estimation of PEO coating barrier properties from slow-strain rate tensile testing. %0 journal article %@ 1996-1944 %A Vaghefinazari, B.,Wierzbicka, E.,Visser, P.,Posner, R.,Arrabal, R.,Matykina, E.,Mohedano, M.,Blawert, C.,Zheludkevich, M.L.,Lamaka, S.V. %D 2022 %J Materials %N 23 %P 8489 %R doi:10.3390/ma15238489 %T Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part III—Corrosion Inhibitors and Combining Them with Other Protection Strategies %U https://doi.org/10.3390/ma15238489 23 %X Owing to the unique active corrosion protection characteristic of hexavalent chromium-based systems, they have been projected to be highly effective solutions against the corrosion of many engineering metals. However, hexavalent chromium, rendered a highly toxic and carcinogenic substance, is being phased out of industrial applications. Thus, over the past few years, extensive and concerted efforts have been made to develop environmentally friendly alternative technologies with comparable or better corrosion protection performance to that of hexavalent chromium-based technologies. The introduction of corrosion inhibitors to a coating system on magnesium surface is a cost-effective approach not only for improving the overall corrosion protection performance, but also for imparting active inhibition during the service life of the magnesium part. Therefore, in an attempt to resemble the unique active corrosion protection characteristic of the hexavalent chromium-based systems, the incorporation of inhibitors to barrier coatings on magnesium alloys has been extensively investigated. In Part III of the Review, several types of corrosion inhibitors for magnesium and its alloys are reviewed. A discussion of the state-of-the-art inhibitor systems, such as iron-binding inhibitors and inhibitor mixtures, is presented, and perspective directions of research are outlined, including in silico or computational screening of corrosion inhibitors. Finally, the combination of corrosion inhibitors with other corrosion protection strategies is reviewed. Several reported highly protective coatings with active inhibition capabilities stemming from the on-demand activation of incorporated inhibitors can be considered a promising replacement for hexavalent chromium-based technologies, as long as their deployment is adequately addressed. %0 journal article %@ 0010-938X %A Chen, Q.,Lu, X.,Serdechnova, M.,Wang, C.,Lamaka, S.,Blawert, C.,Zheludkevich, M.L.,Wang, F. %D 2022 %J Corrosion Science %N %P 110785 %R doi:10.1016/j.corsci.2022.110785 %T Formation of self-healing PEO coatings on AM50 Mg by in-situ incorporation of zeolite micro-container %U https://doi.org/10.1016/j.corsci.2022.110785 %X Ce3+ ions containing zeolite microparticles were in-situ incorporated into plasma electrolytic oxidation (PEO) coating to provide self-healing property for AM50 Mg alloy. It was found that the Ce3+ ions can be released from the inertly incorporated zeolite microparticles via ion-exchange as well as from dissolved coating material which contains high concentration of reactively incorporated zeolites when corrosion occurs, leading to improved corrosion resistance of the oxide layer in 0.5 wt% NaCl solution. The newly formed cerium hydroxides/oxides when corrosion occurs can stabilize and enhance the barrier property of the passive film at metal/coating interface. %0 journal article %@ 1996-1944 %A Vaghefinazari, B.,Wierzbicka, E.,Visser, P.,Posner, R.,Arrabal, R.,Matykina, E.,Mohedano, M.,Blawert, C.,Zheludkevich, M.,Lamaka, S. %D 2022 %J Materials %N 23 %P 8676 %R doi:10.3390/ma15238676 %T Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: PART I—Pre-Treatment and Conversion Coating %U https://doi.org/10.3390/ma15238676 23 %X Corrosion protection systems based on hexavalent chromium are traditionally perceived to be a panacea for many engineering metals including magnesium alloys. However, bans and strict application regulations attributed to environmental concerns and the carcinogenic nature of hexavalent chromium have driven a considerable amount of effort into developing safer and more environmentally friendly alternative techniques that provide the desired corrosion protection performance for magnesium and its alloys. Part I of this review series considers the various pre-treatment methods as the earliest step involved in the preparation of Mg surfaces for the purpose of further anti-corrosion treatments. The decisive effect of pre-treatment on the corrosion properties of both bare and coated magnesium is discussed. The second section of this review covers the fundamentals and performance of conventional and state-of-the-art conversion coating formulations including phosphate-based, rare-earth-based, vanadate, fluoride-based, and LDH. In addition, the advantages and challenges of each conversion coating formulation are discussed to accommodate the perspectives on their application and future development. Several auspicious corrosion protection performances have been reported as the outcome of extensive ongoing research dedicated to the development of conversion coatings, which can potentially replace hazardous chromium(VI)-based technologies in industries. %0 journal article %@ 0013-4686 %A Zhou, Y.,Lu, X.,Zheludkevich, M.,Wang, F. %D 2022 %J Electrochimica Acta %N %P 141471 %R doi:10.1016/j.electacta.2022.141471 %T Tailoring corrosion and discharge performance of Mg anode by corrosion inhibitor %U https://doi.org/10.1016/j.electacta.2022.141471 %X The effect of various amounts of 5-sulfosalicylic acid (SSA) on the corrosion and discharge property of pure magnesium (Mg) is studied systematically. It was found that SSA plays a vital role in regulating the dissolution kinetics of the substrate and re-deposition rate of discharge product at the metal/electrolyte interface. Low concentration of SSA can be used as corrosion inhibitor for active Mg surface as it chelates with impurity element (Fe3+), while high concentration of SSA increases dissolution rate of Mg since large amount of SSA also acts as complexing agent for the dissolved Mg2+. In terms of discharge performance, addition of 0.1 M SSA improves the utilization efficiency and lowers the discharge potential in the meanwhile under different current densities. The anode demonstrates low and stable discharge potential (-1.83 V) for 10 h at 2.5 mA cm−2 in SSA containing electrolyte. Localized corrosion of the substrate has been significantly facilitated during discharge test. “Thorn-like effect” has been observed for the first time for Mg with addition of complexing agent. %0 journal article %@ 0010-938X %A Oliveira, M.P.,Silva, R.M.,Yasakau, K.A.,Bastos, A.,Kallip, S.,Zheludkevich, M.L.,Silva, R.F.,Ferreira, M.G.S. %D 2022 %J Corrosion Science %N %P 110773 %R doi:10.1016/j.corsci.2022.110773 %T Atomic layer deposition of nanometric alumina for corrosion protection of heterogeneous metallic surfaces – The case of aeronautical grade aluminium alloy 2024-T3 %U https://doi.org/10.1016/j.corsci.2022.110773 %X Nanometric layers of Al2O3 were applied by atomic layer deposition (ALD) on 2024-T3 aluminium alloy. The ALD layers suppressed the corrosion of the alloy as confirmed by Scanning Kelvin Probe Force Microscopy (SKPFM), polarization curves and Electrochemical Impedance Spectroscopy (EIS). The protection provided by the ALD layers weakened with the time of immersion and this was attributed to the incorporation of hydroxyl species in the film during the deposition at low temperature (100 °C) making them vulnerable to water. %0 journal article %@ 1996-1944 %A Karlova, P.,Serdechnova, M.,Blawert, C.,Lu, X.,Mohedano, M.,Tolnai, D.,Zeller-Plumhoff, B.,Zheludkevich, M.L. %D 2022 %J Materials %N 18 %P 6315 %R doi:10.3390/ma15186315 %T Comparison of 2D and 3D Plasma Electrolytic Oxidation (PEO)-Based Coating Porosity Data Obtained by X-ray Tomography Rendering and a Classical Metallographic Approach %U https://doi.org/10.3390/ma15186315 18 %X In this work, the porosity of plasma electrolytic oxidation (PEO)-based coatings on Al- and Mg-based substrates was studied by two imaging techniques—namely, SEM and computer microtomography. Two approaches for porosity determination were chosen; relatively simple and fast SEM surface and cross-sectional imaging was compared with X-ray micro computed tomography (microCT) rendering. Differences between 2D and 3D porosity were demonstrated and explained. A more compact PEO coating was found on the Al substrate, with a lower porosity compared to Mg substrates under the same processing parameters. Furthermore, huge pore clusters were detected with microCT. Overall, 2D surface porosity calculations did not show sufficient accuracy for them to become the recommended method for the exact evaluation of the porosity of PEO coatings; microCT is a more appropriate method for porosity evaluation compared to SEM imaging. Moreover, the advantage of 3D microCT images clearly lies in the detection of closed and open porosity, which are important for coating properties. %0 journal article %@ 2050-7488 %A Würger, T.,Wang, L.,Snihirova, D.,Deng, M.,Lamaka, S.,Winkler, D.,Höche, D.,Zheludkevich, M.,Meißner, R.,Feiler, C. %D 2022 %J Journal of Materials Chemistry A %N 40 %P 21672-21682 %R doi:10.1039/D2TA04538A %T Data-driven Selection of Electrolyte Additives for Aqueous Magnesium Batteries %U https://doi.org/10.1039/D2TA04538A 40 %X Aqueous primary Mg-air batteries have considerable potential as energy sources for sea applications and portable devices. However, some challenges at the anode-electrolyte interface related to self-corrosion, aging of the electrolyte and the chunk-effect have to be solved to improve the discharge potential of the battery as well as the utilization efficiency of the anode material. Aside from alloying, an effective strategy to mitigate self-corrosion and battery failure is the use of electrolyte additives. Selecting useful additives from the vast chemical space of possible compounds is not a trivial task. Fortunately, data-driven quantitative structure-property relationship (QSPR) models can facilitate efficient searches for promising battery booster candidates. Here, the robustness and predictive performance of two QSPR models are evaluated using an active design of experiments approach. We also present a multi-objective optimization method that allows to identify new electrolyte additives that can boost the battery anode performance with respect to a target application, thus accelerating the discovery of advanced battery systems. %0 journal article %@ 0352-5139 %A Bozovic, N.,Mojsilovic, K.,Stojanovic, S.,Damjanovic-Vasilic, L.,Serdechnova, M.,Blawert, C.,Zheludkevich, M.,Stojadinovic, S.,Vasilic, R. %D 2022 %J Journal of the Serbian Chemical Society %N 9 %P 1035-1048 %R doi:10.2298/JSC211203058B %T Oxide coatings with immobilized Ce-ZSM5 as visible light photocatalysts %U https://doi.org/10.2298/JSC211203058B 9 %X The preparation and properties of oxide coatings with immobilized ZSM-5 zeolite obtained by plasma electrolytic oxidation on aluminum support were investigated and discussed. Pure and Ce-exchanged ZSM-5 were immo-bilized on aluminum supports from a silicate-based electrolyte under ultra-low duty cycle pulsed direct current conditions. The obtained composite coatings were characterized with respect to their morphology, phase and chemical com-position, as well as photocatalytic activity and anti-corrosion properties. All mentioned properties of the obtained coatings were dependent on the processing time. The coatings with Ce-exchanged ZSM-5 showed higher photocatalytic activity and more effective corrosion protection than those with pure ZSM-5. The highest photocatalytic activity was observed for coatings processed for 30 min. It is suggested that the surface morphology, Ce-content and number of defects influenced the photocatalytic activity of the composite coatings. %0 journal article %@ 2405-8297 %A Wang, L.,Snihirova, D.,Deng, M.,Vaghefinazari, B.,Xu, W.,Höche, D.,Lamaka, S.V.,Zheludkevich, M.L. %D 2022 %J Energy Storage Materials %N %P 573-597 %R doi:10.1016/j.ensm.2022.08.032 %T Sustainable aqueous metal-air batteries: An insight into electrolyte system %U https://doi.org/10.1016/j.ensm.2022.08.032 %X To meet the growing demand for sustainable and endurable energy sources, various novel energy conversion and storage systems have emerged and been developed rapidly over the last decades. Aqueous metal-air batteries have aroused much interest owing to their superior energy density, exceptional reliability, and environmental benignity. Nevertheless, the practical discharge performance of aqueous metal-air batteries is far below that desired. In comparison to the electrode materials design with much effort, relatively minor attention has been paid to the development of electrolyte systems, which undoubtedly is crucial for battery properties. In order to stimulate and promote the development of electrolyte systems for high-performance aqueous metal-air batteries, in-depth insight into the working mechanism of aqueous metal-air batteries and recent advances on electrolytes development are presented in this work. The critical issues that conventional aqueous Zn-air, Al-air, and Mg-air batteries are confronted with are thoroughly discussed, whilst some facile solutions via electrolyte modification recently proposed in the literature are reviewed. An outlook on future research into electrolyte systems for aqueous metal-air batteries is proposed. %0 journal article %@ 0013-4651 %A Bouali, A.C.,Serdechnova, M.,Yasakau, K.A.,Lutz, A.,Wiese, G.,Terryn, H.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2022 %J Journal of the Electrochemical Society %N 8 %P 081501 %R doi:10.1149/1945-7111/ac83f5 %T The Role of Cu-Based Intermetallic on the Direct Growth of a ZnAl LDH Film on AA2024 %U https://doi.org/10.1149/1945-7111/ac83f5 8 %X The direct ZnAl layered double hydroxide growth on AA2024 is a fast-occurring reaction, yet is characterized by an inhomogeneous film thickness. It has been shown that at the periphery of Cu-rich intermetallic, the flakes tend to be larger and denser. A combination of in situ and ex situ measurements were used to monitor the changes in the layered double hydroxide film grown on the regions of intermetallics. Immediately after immersion, an activation of the intermetallic phases is observed due to the dealloying process with an almost immediate film growth. Dealloying is followed by trenching of the adjacent Al matrix leading to an excessive production of large and dense layered double hydroxide flakes at the periphery of the intermetallic. However, the scanning electron microscopy cross-section images revealed that the trenching process leads to defects in the area surrounding the intermetallic. This could weaken the corrosion resistance performance of the layered double hydroxide conversion coating and lead to adhesion failure of consecutive polymer coatings. Nevertheless, this work highlights a few advantages and drawbacks of the layered double hydroxide conversion coatings and pathways to its potential optimization and improvement. %0 journal article %@ 1996-1944 %A Wierzbicka, E.,Vaghefinazari, B.,Mohedano, M.,Visser, P.,Posner, R.,Blawert, C.,Zheludkevich, M.,Lamaka, S.,Matykina, E.,Arrabal, R. %D 2022 %J Materials %N 23 %P 8515 %R doi:10.3390/ma15238515 %T Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing %U https://doi.org/10.3390/ma15238515 23 %X Although hexavalent chromium-based protection systems are effective and their long-term performance is well understood, they can no longer be used due to their proven Cr(VI) toxicity and carcinogenic effect. The search for alternative protection technologies for Mg alloys has been going on for at least a couple of decades. However, surface treatment systems with equivalent efficacies to that of Cr(VI)-based ones have only begun to emerge much more recently. It is still proving challenging to find sufficiently protective replacements for Cr(VI) that do not give rise to safety concerns related to corrosion, especially in terms of fulfilling the requirements of the transportation industry. Additionally, in overcoming these obstacles, the advantages of newly introduced technologies have to include not only health safety but also need to be balanced against their added cost, as well as being environmentally friendly and simple to implement and maintain. Anodizing, especially when carried out above the breakdown potential (technology known as Plasma Electrolytic Oxidation (PEO)) is an electrochemical oxidation process which has been recognized as one of the most effective methods to significantly improve the corrosion resistance of Mg and its alloys by forming a protective ceramic-like layer on their surface that isolates the base material from aggressive environmental agents. Part II of this review summarizes developments in and future outlooks for Mg anodizing, including traditional chromium-based processes and newly developed chromium-free alternatives, such as PEO technology and the use of organic electrolytes. This work provides an overview of processing parameters such as electrolyte composition and additives, voltage/current regimes, and post-treatment sealing strategies that influence the corrosion performance of the coatings. This large variability of the fabrication conditions makes it possible to obtain Cr-free products that meet the industrial requirements for performance, as expected from traditional Cr-based technologies. %0 journal article %@ 0257-8972 %A Kasneryk, V.,Poschmann, M.P.M.,Serdechnova, M.,Dovzhenko, G.,Wieland, D.C.F.,Karlova, P.,Naacke, T.,Starykevich, M.,Blawert, C.,Stock, N.,Zheludkevich, M.L. %D 2022 %J Surface and Coatings Technology %N %P 128733 %R doi:10.1016/j.surfcoat.2022.128733 %T Formation and structure of ZIF-8@PEO coating on the surface of zinc %U https://doi.org/10.1016/j.surfcoat.2022.128733 %X Recently, plasma electrolytic oxidation (PEO) found broad application as a multi-purpose process to create effective corrosion and wear resistant coatings on various metallic substrates. The exceptional properties of metal organic frameworks (MOFs) put them also in focus as perspective materials for corrosion protection. In this work, the formation of a novel ZIF-8@PEO coating is reported for the first time. It was synthesized by controllable recrystallization of a PEO layer formed on zinc alloy Z1 into ZIF-8 in the presence of 2-methylimidazole organic linkers. The multi-stage mechanism of PEO to ZIF-8 rearrangement is proposed. Cross section, glow discharge optical emission spectroscopy and nano-focused synchrotron X-ray diffraction demonstrated that varying of synthesis parameters, the ZIF-8@PEO coating with different distribution of ZIF-8 through PEO layer can be prepared. Based on the results of laser scanning microscopy, the surface smoothing was observed with increasing the degree of the PEO-to-ZIF-8 rearrangement. Containing two components, the novel ZIF-8@PEO coating is expected to combine admirable physical-chemical properties of both PEO and ZIF-8. Such a feature can open the way for its potential application not only for corrosion protection, but also for photo- and heterogeneous catalysis. %0 journal article %@ 0010-938X %A Vaghefinazari, B.,Lamaka, S.V.,Blawert, C.,Serdechnova, M.,Scharnagl, N.,Karlova, P.,Wieland, D.C.F.,Zheludkevich, M.L. %D 2022 %J Corrosion Science %N %P 110344 %R doi:10.1016/j.corsci.2022.110344 %T Exploring the corrosion inhibition mechanism of 8-hydroxyquinoline for a PEO-coated magnesium alloy %U https://doi.org/10.1016/j.corsci.2022.110344 %X In this study, the corrosion inhibition effect of 8-hydroxyquinoline (8HQ) on a PEO-coated AZ21 magnesium alloy is explored. The interaction of 8HQ molecules with both bare AZ21 and PEO layer was thoroughly scrutinized during the exposure to a corrosive NaCl electrolyte using different characterization methods, including EIS, SEM, Raman spectroscopy, and XRD. The corrosion inhibition mechanism stems from the extensive precipitation of the insoluble complex between 8HQ molecules and Mg2+ on top of the PEO layer, which leads to subsequently inhibition-enhancing phenomena, including modification of the corrosion products and re-precipitation of the PEO amorphous phase. %0 journal article %@ 0378-7753 %A Xu, W.,Snihirova, D.,Deng, M.,Wang, L.,Vaghefinazari, B.,Wang, C.,Lamaka, S.V.,Zheludkevich, M.L.,Höche, D. %D 2022 %J Journal of Power Sources %N %P 231745 %R doi:10.1016/j.jpowsour.2022.231745 %T A mathematical model describing the surface evolution of Mg anode during discharge of aqueous Mg-air battery %U https://doi.org/10.1016/j.jpowsour.2022.231745 %X A numerical model is developed, aiming to understand and describe anode dissolution behavior and respective interface effects at an Mg-0.1Ca anode during discharge within an aqueous magnesium-air battery (MAB). In this model, the negative difference effect (NDE) that impairs the performance (e.g. utilization efficiency and capacity) of the anode is considered by adding a linear semi-empirical equation to calculate the total dissolution current density responsible for the dissolution of the Mg-0.1Ca anode. The proposed model is capable of predicting the effect of Mg(OH)2 deposit on the discharge process by consideration of surface coverage, layer thickness, and deposit porosity. In addition, the model can track the pH changes within electrolyte nearby the anode surface during discharge processes. The simulation results representing the development of local pH and the thickness of the deposited layer are validated by corresponding experimental measurements and are in good agreement with the experimental findings. %0 journal article %@ 2397-2106 %A Ofoegbu, S.U.,Quevedo, M.C.,Bastos, A.C.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2022 %J npj Materials Degradation %N 1 %P 49 %R doi:10.1038/s41529-022-00261-1 %T Electrochemical characterization and degradation of carbon fibre reinforced polymer in quiescent near neutral chloride media %U https://doi.org/10.1038/s41529-022-00261-1 1 %X In a quest for a better understanding of the mechanism and contribution(s) of fresh (“un-degraded”) and degraded CFRP surfaces to galvanic corrosion of coupled metals in multi-material assemblies the electrochemical behaviour of CFRP in quiescent 50 mM NaCl was studied using electrochemical techniques. Tests using ferricyanide/ferrocyanide redox couple revealed a quasi-reversible behaviour. Under cathodic polarization, CFRP is active electrochemically evidenced by the increase in pH (to pH ≥ 10). Galvanic current densities and potentials for Al-CFRP couple comprised of freshly polished CFRP sample ranged from 15–25 µA cm−2 and ≈−660 to −850 mVSCE respectively, while the corresponding parameter for Al-CFRP couple comprised of degraded CFRP were in the range 10–25 µA cm−2 and ≈−670 to −900 mVSCE. Contrary to expectations, CFRP prior exposure to degradative high pH media before galvanic coupling did not result in an increase in the intensity of galvanic corrosion of the coupled metal. %0 journal article %@ 2397-2106 %A Galvao, T.,Farreira, I.,Kuznetsova, A.,Novell-Leruth, G.,Song, C.,Feiler, C.,Lamaka, S.,Rocha, C.,Maia, F.,Zheludkevich, M.,Gomes, J.,Tedim, J. %D 2022 %J npj Materials Degradation %N %P 48 %R doi:10.1038/s41529-022-00259-9 %T CORDATA: an open data management web application to select corrosion inhibitors %U https://doi.org/10.1038/s41529-022-00259-9 %X The ban of one of industry’s main solutions against corrosion, i.e. compounds based on hexavalent chromium1, has recently started in Europe due to health and environmental issues, resulting in a need to find effective replacements2. The large and growing amounts of reported corrosion inhibition efficiencies existing in literature and obtained over the years as a result of this event is expected to keep increasing in volume. Moreover, the development of high-throughput testing methodologies3,4,5,6,7,8, has allowed to obtain significant databases in shorter timeframes for different substrates, application conditions and molecular structures3,9,10. This has called for the development of a data driven application, such as the one developed in this work, which will allow academic and industry researchers to swiftly select the most adequate condition specific corrosion inhibitor to be embedded directly into protective coating systems or through smart nanocontainers. We envision the CORDATA app to be the first step in the corrosion inhibitor selection process before going to the laboratory to perform further research and development activities. Although there are many accounts in literature focusing on corrosion inhibition efficiencies, to the best of our knowledge, this is the first web application dealing with data management for this particular issue. It allows to more efficiently compare many different data sources at the same time, thus making it easier to find appropriate solutions that were already tested experimentally, but that might be lost in the middle of a large volume of experimental data obtained in the past. Moreover, the dynamic nature of a data management web application, will allow it to grow in size and evolve in functionality throughout the years, adapting to the needs of the corrosion science community to better solve societal challenges through open data. %0 journal article %@ 0300-9440 %A Korrapati, V.,Scharnagl, N.,Letzig, D.,Zheludkevich, M. %D 2022 %J Progress in Organic Coatings %N %P 106608 %R doi:10.1016/j.porgcoat.2021.106608 %T Bilayer coatings for temporary and long–term corrosion protection of magnesium–AZ31 alloy %U https://doi.org/10.1016/j.porgcoat.2021.106608 %X Phosphate and silane containing organic self–assembled (SA) layers serve as pre–treatments on magnesium alloy sheet materials. A reliable protection was achieved in this work via application of alkyd–based coatings on the pretreated surface. The idea of adopting SA pre–treatments as functional layers at metal–polymer interface is to influence the adhesive properties between solid metal substrate and alkyd–based coating. Hexadecyltrimethoxysilane (HDTMS) deposited metal surfaces exhibit stronger adhesive strength, while a near homogeneous distribution of the octadecylphosphonic acid (ODPA) and perfluorodecylphosphonic acid (PFDPA) exhibit low adhesive phenomenon, when placed as pre–layers in bilayer coatings. Electrochemical impedance results after 168 h of immersion reveal that the organophosphate and organosilane deposited bilayer films demonstrate protective properties with almost no interface defects. Moreover, organophosphate treated bilayer coatings enhance easy peeling of alkyd coat after protecting the surface from corrosive electrolytes. Bilayer coatings developed on AZ31 sheets can confer temporary or long–term corrosion protection depending on further processing strategy and offer efficient alloy protection for both purposes. %0 journal article %@ 0169-4332 %A Wu, T.,Blawert, C.,Serdechnova, M.,Karlova, P.,Dovzhenko, G.,Florian Wieland, D.C.,Stojadinovic, S.,Vasilic, R.,Wang, L.,Wang, C.,Mojsilovic, K.,Zheludkevich, M.L. %D 2022 %J Applied Surface Science %N %P 153523 %R doi:10.1016/j.apsusc.2022.153523 %T Role of phosphate, silicate and aluminate in the electrolytes on PEO coating formation and properties of coated Ti6Al4V alloy %U https://doi.org/10.1016/j.apsusc.2022.153523 %X A comparison of PEO layers on Ti6Al4V alloy formed in phosphate, aluminate and silicate-based electrolytes respectively, has been made to reveal the influence of the electrolyte composition on the formation process. The phosphate-based electrolyte has been identified as the most promising one as it has the best coating formation efficiency and the lowest breakdown voltage. On the bases of the microstructure and elemental/phase analysis of the different PEO coatings, it could be observed that the PEO coating formed in phosphate-based electrolyte is mainly composed of anatase and rutile. An amorphous phase is dominant in the coating produced in silicate-based electrolyte. Moreover, there are mainly γ-Al2O3, Na2Al2xO3x+1 and TiAl2O5 present in the coating formed in the aluminate-based electrolyte. The coating formation process in silicate- and aluminate-based electrolytes is more dependent on the deposition originating from the electrolytes. All of the coatings have shown noticeable corrosion resistance and good performance in the photocatalytic test as the degradation rates of methyl orange higher than 45 %. Thus, multifunctional PEO coatings on Ti6Al4V alloy are obtained. %0 journal article %@ 0010-938X %A Charalampidou, C.,Dietzel, W.,Zheludkevich, M.,Kourkoulis, S.,Alexopoulos, N. %D 2021 %J Corrosion Science %N %P 109330 %R doi:10.1016/j.corsci.2021.109330 %T Corrosion-induced mechanical properties degradation of Al-Cu-Li (2198-T351) aluminium alloy and the role of side-surface cracks %U https://doi.org/10.1016/j.corsci.2021.109330 %X Corrosion-induced surface deterioration as well as mechanical properties degradation of AA2198-T351 were experimentally investigated and compared against AA2024-T3. Pre-corroded tensile and fatigue specimens were mechanically tested. Several degradation mechanisms were detected for different exposure times: a) pitting formation for short exposure times, where AA2198-T351 is superior to AA2024-T3 regarding corrosion resistance, b) exfoliation corrosion for higher exposure times (> 24 h), where almost the same corrosion resistance, regarding tensile elongation at fracture Af decrease, is evident for the two alloys and c) delamination between the grain layers on the side-surfaces. The fatigue endurance limit of AA2198-T351 was almost halved after 6 h corrosion exposure. Side-surfaces corrosion-induced cracks play a pivotal role on the Af decrease of AA2024-T3 due to delamination between the grain layers in the longitudinal rolling direction while this was not observed for AA2198-T351. %0 journal article %@ 2192-2659 %A Gonzalez, J.,Lamaka, S.,Mei, D.,Scharnagl, N.,Feyerabend, F.,Zheludkevich, M.,Willumeit-Römer, R. %D 2021 %J Advanced Healthcare Materials %N 13 %P 2100053 %R doi:10.1002/adhm.202100053 %T Mg Biodegradation Mechanism Deduced from the Local Surface Environment under Simulated Physiological Conditions %U https://doi.org/10.1002/adhm.202100053 13 %X Although certified magnesium-based implants are launched some years ago, the not well-defined Mg degradation mechanism under physiological conditions makes it difficult to standardize its use as a degradable biomaterial for a wide range of implant applications. Among other variables influencing the Mg degradation mechanism, monitoring the pH in the corrosive solution and, especially, at the corroding interface is important due to its direct relation with the formation and stability of the degradation products layer. The interface pH (pH at the Mg/solution interface) developed on Mg-2Ag and E11 alloys are studied in situ during immersion under dynamic conditions (1.5 mL min-1) in HBSS with and without the physiological amount of Ca2+ cations (2.5 × 10-3 m). The results show that the precipitation/dissolution of amorphous phosphate-containing phases, that can be associated with apatitic calcium-phosphates Ca10-x(PO4)6-x(HPO4 or CO3)x(OH or ½ CO3)2-x with 0 ≤ x ≤ 2 (Ap-CaP), promoted in the presence of Ca2+ generates an effective local pH buffering system at the surface. Thus, high alkalinization is prevented, and the interface pH is stabilized in the range of 7.6 to 8.5. %0 journal article %@ 1932-7447 %A Bouali, A.,Iuzviuk, M.,Serdechnova, M.,Yasakau, K.,Drozdenko, D.,Lutz, A.,Fekete, K.,Dovzhenko, G.,Wieland, F.,Terryn, H.,Ferreira, M.,Zobkalo, I.,Zheludkevich, M. %D 2021 %J The Journal of Physical Chemistry C %N 21 %P 11687-11701 %R doi:10.1021/acs.jpcc.1c02281 %T Mechanism of LDH Direct Growth on Aluminum Alloy Surface: A Kinetic and Morphological Approach %U https://doi.org/10.1021/acs.jpcc.1c02281 21 %X The growth of ZnAl layered double hydroxide (LDH) on the AA2024 surface was monitored using synchrotron high-resolution X-ray diffraction. Data were analyzed using the Avrami–Erofe’ev kinetic model. Accordingly, the LDH film growth is governed by a two-dimensional (2D) diffusion-controlled reaction with a zero nucleation rate. Additional methods, including ex situ atomic force microscopy/scanning Kelvin probe force microscopy (AFM/SKPFM) supported by in situ open-circuit potential (OCP) measurements together with scanning electron microscopy (SEM) and transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM/EDX) analysis, provided further insight into the different stages of the mechanism of LDH growth. Prior to the conversion coating formation, an intermediate layer is formed as a basis for the establishment of the LDH flakes. Moreover, a Cu-rich layer was revealed, which could contribute to the acceleration of LDH growth. The formed LDH layer does not show any cracks at the interface but presents minor irregularities in the structure, which could favor adhesion to subsequent organic coatings. The findings presented in this work provide an important insight to the corrosion performance of the LDH conversion coatings and the pathway to adopt for further optimization. %0 journal article %@ 0010-938X %A Wang, L.,Snihirova, D.,Deng, M.,Wang, C.,Vaghefinazari, B.,Wiese, G.,Langridge, M.,Höche, D.,Lamaka, S.,Zheludkevich, M. %D 2021 %J Corrosion Science %N %P 109501 %R doi:10.1016/j.corsci.2021.109501 %T Insight into physical interpretation of high frequency time constant in electrochemical impedance spectra of Mg %U https://doi.org/10.1016/j.corsci.2021.109501 %X Electrochemical impedance spectroscopy measurements were performed to study the evolution of surface condition, which related to the high frequency time constant of Mg, in 0.05 M NaCl solution at three different pH. Based on the assumption that the high frequency time constant originates solely from the surface film, the thickness of MgO film was calculated via fitting EIS results. The deduced results were compared with the actual surface condition, characterized by transmission electron microscopy and local measurements. The results verified that the time constant at the high frequency range originates from the barrier properties of the surface film. %0 journal article %@ 1005-0302 %A Wu, Y.,Wu, L.,Zheludkevich, M.,Chen, Y.,Serdechnova, M.,Yao, W.,Blawert, C.,Atrens, A.,Pan, F. %D 2021 %J Journal of Materials Science & Technology %N %P 28-39 %R doi:10.1016/j.jmst.2021.03.011 %T MgAl-V2O7 4- LDHs/(PEI/MXene)10 composite film for magnesium alloy corrosion protection %U https://doi.org/10.1016/j.jmst.2021.03.011 %X In this study, MgAl-V2O74- LDHs/(poly(ethyleneimine)(PEI)/MXene)n composite films were synthesized via (i) in-situ hydrothermal growth of Mg-Al layered double hydroxides (LDHs) on AZ31 alloy followed by vanadate intercalation reactions, and (ii) the as-prepared MgAl-V2O74- LDHs film was covered by layer-by-layer assembly using (PEI/MXene)n, where n=5, 10, and 20. Film characterization revealed that the outer layers (PEI/MXene) were assembled on the surface by electrostatic interaction and provided a good coverage of LDHs nanosheets. But, microcracks appeared gradually on the surface and destroyed the film integrity with increasing number of PEI/MXene layers. The corrosion tests indicated that the MgAl-V2O74- LDHs/(PEI/MXene)10 composite films provided a better corrosion protection ability than that of n=5 and 20. The outer layers (PEI/MXene) had a corrosion inhibition protective effect on MgAl-V2O74- LDHs film. This work opened a new perspective of the MXene materials for anticorrosion application via a layer-by-layer assembly method. %0 journal article %@ 0010-938X %A Gnedenkov, A.,Lamaka, S.,Sinebryukhov, S.,Mashtalyar, D.,Egorkin, V.,Imshinetskiy, I.,Zheludkevich, M.,Gnedenkov, S. %D 2021 %J Corrosion Science %N %P 109254 %R doi:10.1016/j.corsci.2021.109254 %T Control of the Mg alloy biodegradation via PEO and polymer-containing coatings %U https://doi.org/10.1016/j.corsci.2021.109254 %X The composite calcium-phosphate coating on MA8 Mg alloy consisting of the inorganic porous basis sealed with polymer is suggested. To control the alloy resorption kinetics, the coating obtained by plasma electrolytic oxidation is modified with superdispersed polytetrafluoroethylene using electrophoretic deposition (EPD). Protective properties and morphology evolution as a result of surface treatment and corrosion propagation are examined by EIS, PDP, hydrogen evolution tests, SEM, EDX and XRD analysis. The obtained coatings are investigated at mechanistic level using SVET and local pH measurements. EPD composite coating decreases electrochemical activity of the sample in minimum essential medium and ensures the material biocompatibility. %0 journal article %@ 2051-6347 %A Deng, M.,Wang, L.,Höche, D.,Lamaka, S.,Wang, C.,Snihirova, D.,Jin, Y.,Zhang, Y.,Zheludkevich, M. %D 2021 %J Materials Horizons %N 2 %P 589-596 %R doi:10.1039/d0mh01380c %T Approaching “stainless magnesium” by Ca micro-alloying %U https://doi.org/10.1039/d0mh01380c 2 %X Severe corrosion of Mg and Mg alloys is a major issue hindering their wider application in transportation industry, medical implants and aqueous batteries. Previously, no Mg-based material has been found with a significantly lower corrosion rate than that of ultra-high-purity Mg, i.e. 0.25 mm y−1 in concentrated NaCl solution. In this work for the first time, highly corrosion-resistant Mg is found to be accomplishable by Ca micro-alloying, bringing “stainless Mg” closer. The designed Mg–Ca lean alloys possess incredibly low corrosion rates, less than 0.1 mm y−1 in 3.5 wt% NaCl solution, which are significantly lower than that of ultra-high-purity Mg and all Mg alloys reported thus far. The outstanding corrosion resistance is attributed to inhibition of cathodic water reduction kinetics, impurities stabilizing and a protective surface film induced by Ca micro-alloying. Combined with the environmental benignity and economic viability, Ca micro-alloying renders huge feasibility on developing advanced Mg-based materials for diverse applications. %0 journal article %@ 0013-4686 %A Yasakau, K.,Starykevich, M.,Ferreira, M.,Zheludkevich, M. %D 2021 %J Electrochimica Acta %N %P 138091 %R doi:10.1016/j.electacta.2021.138091 %T A critical look at interpretation of electrochemical impedance spectra of sol-gel coated aluminium %U https://doi.org/10.1016/j.electacta.2021.138091 %X A proper assignment of time constants is important for the correct interpretation of the electrochemical impedance spectra of coated substrates. In this work, several model aluminium samples with different anodic oxide thicknesses were prepared and characterised. The aluminium samples were coated by a hybrid sol-gel formulation and studied by electrochemical impedance spectroscopy (EIS) during immersion in NaCl solution. A hierarchical model containing three R-C elements adequately described the impedance spectra of the coated samples. The R-C elements described the properties of sol-gel coatings, aluminium oxide layers and corrosion process. The contribution of the aluminium oxide layer to impedance was unambiguously proven to be at middle frequencies on the spectra. Furthermore, the “real” capacitances of oxide layers were obtained from two capacitance–CPE equations and their applicability was scrutinized. The obtained results presented an opportunity to determine the adhesion behaviour of the sol-gel coatings to the oxide layers, which was studied by analysing the ratio of the oxide layer capacitance of the sol-gel coated samples to the capacitance of the uncoated ones. It was demonstrated that the exposed surface area of the oxide to the electrolyte was about 60–68% and was not changing during immersion. Based on these findings, a degradation model of the sol-gel coating on anodised aluminium was proposed. %0 journal article %@ 0013-4686 %A Wang, L.,Snihirova, D.,Deng, M.,Wang, C.,Höche, D.,Lamaka, S.,Zheludkevich, M. %D 2021 %J Electrochimica Acta %N %P 137916 %R doi:10.1016/j.electacta.2021.137916 %T Indium chloride as an electrolyte additive for primary aqueous Mg batteries %U https://doi.org/10.1016/j.electacta.2021.137916 %X Indium chloride (InCl3) as an electrolyte additive for primary aqueous Mg batteries is evaluated in this work in terms of its effect on discharge potential, self-corrosion rate and utilization efficiency of a newly developed Mg-0.15Ca anode. InCl3 addition to aqueous electrolyte leads to a more negative discharge potential but the enhancement weakens along with the consumption of In3+ to form In(OH)3 precipitates during the discharge process. Utilization efficiency of the anode is increased by adding InCl3 due to uniform anodic dissolution and suppressed self-corrosion with reduced chunk effect. Mg-air battery test results indicate that 10 mM InCl3 as electrolyte additive significantly enhances the cell voltage of aqueous Mg-air battery to 1.74 V and the specific energy based on anode weight loss to 2.26 kWh/ kg at 1 mA cm−2. %0 journal article %@ 1438-1656 %A Ignjatovic, S.,Blawert, C.,Serdechnova, M.,Karpushenkov, S.,Damjanovic, M.,Karlova, P.,Dovzhenko, G.,Wieland, F.,Zeller-Plumhoff, B.,Starykevich, M.,Stojanovic, S.,Damjanovic-Vasilic, L.,Zheludkevich, M. %D 2021 %J Advanced Engineering Materials %N 6 %P 2001527 %R doi:10.1002/adem.202001527 %T The Influence of In Situ Anatase Particle Addition on the Formation and Properties of Multifunctional Plasma Electrolytic Oxidation Coatings on AA2024 Aluminum Alloy %U https://doi.org/10.1002/adem.202001527 6 %X Plasma electrolytic oxidation (PEO) with in‐situ anatase particle addition was applied to functionalize the surface of AA2024 alloy. A base potassium titanium‐oxide oxalate dihydrate aqueous electrolyte was used with up to 30 g/L anatase particle addition. The coatings’ morphology and phase composition as a function of the anatase concentration in the electrolyte were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and glow discharge optical emission spectroscopy (GDOES). Photocatalytic activity, stability in chloride solution and tribological properties were also determined. The main coating forming phases are anatase and rutile on top of a mixed interface region consisting of TiAl2O5 as reaction product between the TiO2 and an Al2O3 barrier layer on top of the Al substrate. The mixed layer is extending with increasing amount of particles added, due to intensified discharges. In addition, anatase to rutile phase ratio increases due to the additional anatase particles in the electrolyte. Thus, the photocatalytic activity is improving with the particle addition. The coatings’ mechanical resistance is dropping first before increasing again with more particles added. Chemical and restored mechanical stability seems to be related to the extended mixed interface formation, which strengthen the bond to the substrate when more particles are added. %0 journal article %@ 2624-5558 %A Mir, Z.,Gomes, C.,Bastos, A.,Sampaio, R.,Maia, F.,Rocha, C.,Tedim, J.,Höche, D.,Ferreira, M.,Zheludkevich, M. %D 2021 %J Corrosion and Materials Degradation %N 1 %P 78-99 %R doi:10.3390/cmd2010005 %T The Stability and Chloride Entrapping Capacity of ZnAl-NO2 LDH in High-Alkaline/Cementitious Environment %U https://doi.org/10.3390/cmd2010005 1 %X In this work, the ZnAl-NO2 LDH (layered double hydroxide) is investigated as a possible additive for mitigating the chloride-induced corrosion of steel in reinforced concrete. The investigation focused on the stability and chloride binding capacity of this LDH in the pH range typical of cementitious materials. Until pH = 12.5 the material was stable and effective in capturing chloride ions from the surrounding aqueous environment. For higher pH, precisely that of hydrated cement, the LDH was partially dissolved and OH− preferentially entrapped instead of Cl−. These results suggested that ZnAl-NO2 has excellent chloride entrapping capability at neutral pH, but this is reduced with increasing pH. However, when the LDH was incorporated into mortars, the chloride ingress was delayed, signifying that the dissolution of LDH leads to a secondary mechanism responsible for chloride capture. %0 journal article %@ 0257-8972 %A Serdechnova, M.,Blawert, C.,Karpushenkov, S.,Karpushenkava, L.,Shulha, T.,Karlova, P.,Vasilic, R.,Stojadinovic, S.,Stojanovic, S.,Damjanovic-Vasilic, L.,Heitmann, V.,Rabchynski, S.,Zheludkevich, M. %D 2021 %J Surface and Coatings Technology %N %P 126948 %R doi:10.1016/j.surfcoat.2021.126948 %T Properties of ZnO/ZnAl2O4 composite PEO coatings on zinc alloy Z1 %U https://doi.org/10.1016/j.surfcoat.2021.126948 %X Recently the successful formation of PEO coatings on zinc alloy in a phosphate aluminate electrolyte was shown. The produced composite coatings contain various mixtures of ZnO and ZnAl2O4. In frame of the current study, the properties of the formed coatings including adhesion/cohesion, wear, corrosion and photocatalytic activity were analysed to identify possible applications. However, the coatings show internal porosity and a sponge-like structure. Thus the cohesion within the coating is quite low. Pull-off tests have demonstrated clear rupture within the PEO layer at strength values as low as 1 MPa. The photocatalytic activity is limited, in spite of the formation of a higher amount of ZnO at shorter treatment times. Interestingly, the composite coatings of ZnO and higher amounts of ZnAl2O4 spinel showed a higher activity, but not sufficient for fast and effective catalytic cleaning applications. %0 journal article %@ 0169-4332 %A Ignjatović, S.,Blawert, C.,Serdechnova, M.,Karpushenkov, S.,Damjanović, M.,Karlova, P.,Wieland, D.C.F.,Starykevich, M.,Stojanović, S.,Damjanović-Vasilić, L.,Zheludkevich, M.L. %D 2021 %J Applied Surface Science %N %P 148875 %R doi:10.1016/j.apsusc.2020.148875 %T Formation of multi-functional TiO2 surfaces on AA2024 alloy using plasma electrolytic oxidation %U https://doi.org/10.1016/j.apsusc.2020.148875 %X Plasma electrolytic oxidation (PEO) was applied to functionalise the surface of AA2024 alloy. A potassium titanium-oxide oxalate dihydrate based aqueous electrolyte was used, which allowed the direct formation of a TiO2 surface layer on the aluminium alloy substrate. The effect of PEO treatment time and the additional presence of anatase particles in the electrolyte solution on the surface layer and its properties (corrosion, wear and photocatalytic activity) were investigated.,It was found that the coating thickness and surface morphology are strongly dependent on the PEO processing time. However, the phase composition is not much affected by the treatment time and the main coating phase is rutile with a smaller amount of anatase. Adding additional anatase in the form of particles increases the amount of anatase in the coatings. The additional particle addition has only minor effect on the corrosion resistance, but reduces the wear resistance remarkably. Interestingly, the addition of anatase particles and the PEO treatment time are not effective in increasing the photocatalytic activities of the samples. %0 journal article %@ 0010-938X %A Wierzbicka, E,,Vaghefinazari, B,,Lamaka, S.V,,Zheludkevich, M.L,,Mohedano, M,,Moreno, L,,Visser, P,,Rodriguez, A,,Velasco, J,,Arrabal, R,,Matykina, E. %D 2021 %J Corrosion Science %N %P 109189 %R doi:10.1016/j.corsci.2020.109189 %T Flash-PEO as an alternative to chromate conversion coatings for corrosion protection of Mg alloy %U https://doi.org/10.1016/j.corsci.2020.109189 %X In the present work, a flash-PEO coating is developed on AZ31B alloy in a combination of silicate, phosphate, and fluoride based electrolyte in order to offer a green alternative to chromate conversion coatings. Multilevel active protection is achieved through synergetic combination of self-sealing effect of PEO coating itself and active inhibition provided by an organic inhibitor impregnated in PEO pores in a post-treatment step. The results indicate that flash-PEO coatings, loaded with organic corrosion inhibitors, can be recommended for exploitation on industrial level as an equally effective corrosion protection system alternative to CCC for paint-bearing and paint-free applications. %0 journal article %@ 0010-9312 %A Feiler, C.,Mei, D.,Luthringer, B.,Lamaka, S.,Zheludkevich, M. %D 2021 %J Corrosion %N 2 %P 204-208 %R doi:10.5006/3597 %T Rational Design of Effective Mg Degradation Modulators %U https://doi.org/10.5006/3597 2 %X Prerequisite to unlock the full potential of Mg-based materials is to gain control of its degradation properties. Here we present a proof of concept for an efficient and robust alternative to the data-driven machine learning approaches that are currently on the rise to facilitate the discovery of corrosion modulating agents. The electronic properties of bipyridine were tuned by its substitution with electron donating and electron withdrawing functional groups to regulate the degradation modulators interaction with different ions and the effect on the corrosion inhibition of pure Mg was predicted based on density functional theory calculations. Bipyridine and two of its derivatives were subsequently investigated experimentally to validate the trend predicted by the quantum chemical calculations. %0 journal article %@ 2397-2106 %A Würger, T.,Mei, D.,Vaghefinazari, B.,Winkler, D.,Lamaka, S.,Zheludkevich, M.,Meißner, R.,Feiler, C. %D 2021 %J npj Materials Degradation %N 1 %P 2 %R doi:10.1038/s41529-020-00148-z %T Exploring structure-property relationships in magnesium dissolution modulators %U https://doi.org/10.1038/s41529-020-00148-z 1 %X Small organic molecules that modulate the degradation behavior of Mg constitute benign and useful materials to modify the service environment of light metal materials for specific applications. The vast chemical space of potentially effective compounds can be explored by machine learning-based quantitative structure-property relationship models, accelerating the discovery of potent dissolution modulators. Here, we demonstrate how unsupervised clustering of a large number of potential Mg dissolution modulators by structural similarities and sketch-maps can predict their experimental performance using a kernel ridge regression model. We compare the prediction accuracy of this approach to that of a prior artificial neural networks study. We confirm the robustness of our data-driven model by blind prediction of the dissolution modulating performance of 10 untested compounds. Finally, a workflow is presented that facilitates the automated discovery of chemicals with desired dissolution modulating properties from a commercial database. We subsequently prove this concept by blind validation of five chemicals. %0 journal article %@ 0924-0136 %A Bouali, A.,André, N.,Silva Campos, M.,Serdechnova, M.,Dos Santos, J.,Amancio-Filho, S.,Zheludkevich, M. %D 2021 %J Journal of Materials Processing Technology %N %P 197-210 %R doi:10.1016/j.jmst.2020.06.038 %T Influence of LDH conversion coatings on the adhesion and corrosion protection of friction spot-joined AA2024-T3/CF-PPS %U https://doi.org/10.1016/j.jmst.2020.06.038 %X Layered double hydroxide (LDH) conversion coatings loaded with corrosion inhibitors were suggested for the surface treatment of the aluminum alloy 2024-T3, prior to friction spot joining with carbon-fiber reinforced polyphenylene sulfide (AA2024-T3/CF-PPS). Vanadate was used as a model corrosion inhibitor. Lap shear testing method revealed an increase of 15% of the joint’s adhesion performance when treated with LDH and before exposure to salt spray. The evaluation of the joints after exposure to salt spray demonstrated a significant difference in the corrosion behavior of the joints when the AA2024-T3 is treated with LDH loaded with nitrate and vanadate species. The LDH intercalated with nitrate revealed a clear improvement in the mechanical and corrosion resistance performance of the joints, even after 6 weeks of salt spray. However, the LDH intercalated with vanadate failed in providing protection against corrosion as well as preserving the mechanical properties of the joints. The effect of the galvanic corrosion was further investigated by zero resistance ammeter measurements as well as localized scanning vibrating electrode technique. %0 journal article %@ 2213-9567 %A Mei, D.,Wang, C.,Lamaka, S.,Zheludkevich, M. %D 2021 %J Journal of Magnesium and Alloys %N 3 %P 805-817 %R doi:10.1016/j.jma.2020.07.002 %T Clarifying the influence of albumin on the initial stages of magnesium corrosion in Hank's balanced salt solution %U https://doi.org/10.1016/j.jma.2020.07.002 3 %X The corrosion behavior of Mg, a promising biodegradable metallic material, in protein-containing pseudophysiological environment is still not fully understood. In this work, the influence of albumin on the corrosion behavior of commercially pure magnesium (CP Mg) is investigated during short-term tests in Hank's Balanced Salt Solution (HBSS). This work focuses on the reactions at the Mg/medium interface from the perspective of the interactions among albumin, media components and substrate. Hydrogen evolution tests demonstrate that the physiological amount of albumin (40 g L−1) accelerates Mg corrosion in HBSS during the first few hours but slows down the degradation afterwards. The presence of albumin decreases the concentration of free Ca2+ in HBSS and delays formation of protective co-precipitation products on Mg surface. The evolution of local pH (differs from typically monitored bulk pH) near Mg/medium interface in albumin-containing HBSS is reported for the first time. Comparison of local and bulk pH values elucidates the pH buffering effect of albumin during the immersion period. Based on these results, adsorption, chelating and pH buffering effects are summarized as three important aspects of albumin influence on Mg corrosion. Additionally, constant replenishment of medium components is shown to be an influential factor during the Mg corrosion tests. %0 journal article %@ 2468-0230 %A Mojsilović, K.,Božović, N.,Stojanović, S.,Damjanović-Vasilić, L.,Serdechnova, M.,Blawert, C.,Zheludkevich, M.L.,Stojadinović, S.,Vasilić, R. %D 2021 %J Surfaces and Interfaces %N %P 101307 %R doi:10.1016/j.surfin.2021.101307 %T Zeolite-containing photocatalysts immobilized on aluminum support by plasma electrolytic oxidation %U https://doi.org/10.1016/j.surfin.2021.101307 %X The preparation and properties of zeolite-containing oxide coatings obtained by plasma electrolytic oxidation are investigated and discussed. Pure and Ce-exchanged natural (clinoptilolite) and synthetic (13X) zeolites are immobilized on aluminum support from silicate-based electrolyte. Obtained coatings are characterized with respect to their morphology, phase and chemical composition, photocatalytic activity and anti-corrosion properties. It is observed that all mentioned properties of obtained coatings are dependent on processing time and type of immobilized zeolite. Coatings with Ce-exchanged zeolite show higher photocatalytic activity and more effective corrosion protection than those with pure zeolite. The highest photocatalytic activity is observed for coatings processed in a pulsed DC regime for 30 min containing Ce-exchanged 13X zeolite, followed by those containing Ce-exchanged clinoptilolite. Pronounced anti-corrosion properties feature almost all samples containing Ce-exchanged 13X zeolite. %0 journal article %@ 2452-199X %A Tonna, C.,Wang, C.,Mei, D.,Lamaka, S.,Zheludkevich, M.,Buhagiar, J. %D 2021 %J Bioactive Materials %N %P 426-440 %R doi:10.1016/j.bioactmat.2021.05.048 %T Biodegradation behaviour of Fe-based alloys in Hanks’ Balanced Salt Solutions: Part I. material characterisation and corrosion testing %U https://doi.org/10.1016/j.bioactmat.2021.05.048 %X Research on Fe-based biodegradable alloys for implant applications has increased considerably over the past decade. However, there is limited information on the influence of testing electrolytes on corrosion product formation and general corrosion progress. In this work, the effect of Hanks’ Balanced Salt Solution (HBSS) with or without Ca2+ on the corrosion of Fe, Fe35Mn and (Fe35Mn)5Ag powder-processed coupons has been studied using potentiodynamic polarisation, Electrochemical Impedance Spectroscopy (EIS), and preliminary localised measurement of pH and dissolved oxygen concentration in close proximity to the metal surface. Both Fe35Mn and (Fe35Mn)5Ag alloys showed accelerated corrosion when compared to pure Fe based on potentiodynamic testing results, with FeMnAg exhibiting the highest corrosion rate in Ca2+-containing HBSS. The results indicate that in Ca2+-containing HBSS, the formation of a partially protective Ca/P layer decelerates the corrosion progress, whereas the Fe- and Mn-phosphates formed in Ca2+-free HBSS do not have the same effect. The Ca/P layer on (Fe35Mn)5Ag experienced a reduction in resistance following several hours of testing, indicating partial loss of its protective effect. %0 journal article %@ 2624-5558 %A Hejjaj, C.,Aghzzaf, A.,Scharnagl, N.,Makha, M.,Dahbi, M.,Zheludkevich, M.,Hakkou, R.,Fischer, C. %D 2021 %J Corrosion and Materials Degradation %N 4 %P 666-677 %R doi:10.3390/cmd2040036 %T Effect of 6-Aminohexanoic Acid Released from Its Aluminum Tri-Polyphosphate Intercalate (ATP-6-AHA) on the Corrosion Protection Mechanism of Steel in 3.5% Sodium Chloride Solution %U https://doi.org/10.3390/cmd2040036 4 %X A new corrosion inhibitor called ATP-6-AHA was elaborated, and its inhibition action on S235 low carbon steel in 3.5% sodium chloride (NaCl) was investigated using gravimetry, potentiodynamic polarization (PP), and electrochemical impedance spectroscopy (EIS). The release of ecofriendly 6-aminohexanoic acid (6-AHA) from its established aluminum tri-polyphosphate intercalate (ATP-6-AHA) is investigated using electrochemical and surface characterization techniques such as X-ray diffraction (XRD) and X-ray fluorescence (XRF). The results revealed that ATP-6-AHA is a good inhibitor, with an inhibition efficiency of approximately 70%. The efficiency is related to the passivation of a steel surface by a phosphate protective layer due to the synergistic effect of 6-AHA, as confirmed by a steel surface analysis conducted using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). This study suggests that the intercalation of 6-AHA as a sustainable organic molecule within the interlayer spaces of aluminum tri-polyphosphate can well serve as a good flaky inhibitor for protecting S235 low-carbon steel from corrosion in 3.5% NaCl. %0 journal article %@ 2213-9567 %A Wu, T.,Blawert, C.,Lu, X.,Serdechnova, M.,Zheludkevich, M. %D 2021 %J Journal of Magnesium and Alloys %N 5 %P 1725-1740 %R doi:10.1016/j.jma.2021.03.017 %T Difference in formation of plasma electrolytic oxidation coatings on MgLi alloy in comparison with pure Mg %U https://doi.org/10.1016/j.jma.2021.03.017 5 %X In order to study the substrate lattice structure (Li addition) on the growth of plasma electrolytic oxidation (PEO) coatings, MgLi alloy (11.36 wt.% of Li, cubic) and pure Mg (hexagonal) were treated under a pulsed direct PEO mode in a phosphate electrolyte for different periods of time. The results revealed that the presence of Li and Li-rich phases in the cubic Mg alloy seems to be essential for the treatment result rather than the original lattice structure. A modified discharge behavior of MgLi alloy finally led to a different microstructure of the coating. The unstable coatings of MgLi alloy tended to dissolve rapidly though shared the similar composition to that of pure Mg. Li was incorporated only in the primary conversion products at the interface of coating/MgLi. In spite of the advanced efficiency of energy input during processing, the more porous and thinner PEO coatings on the MgLi alloy were less resistant to abrasion and corrosion. %0 journal article %@ 0257-8972 %A Wu, T.,Blawert, C.,Serdechnova, M.,Karlova, P.,Dovzhenko, G.,Wieland, F.,Zheludkevich, M. %D 2021 %J Surface and Coatings Technology %N %P 127890 %R doi:10.1016/j.surfcoat.2021.127890 %T Role of polymorph microstructure of Ti6Al4V alloy on PEO coating formation in phosphate electrolyte %U https://doi.org/10.1016/j.surfcoat.2021.127890 %X In this work, the formation behavior of PEO coatings on polymorph Ti6Al4V alloy with two different lattice structures (hexagonal close packed α-Ti and cubic body centered β-Ti phases) was studied, using two galvanostatically controlled processes. The phase formation as a function of treatment time was studied ex-situ locally on the two Ti phases by interrupting the treatment after certain time intervals and in-situ continuously in an integral manner by recording diffraction patterns from the changing surface during the PEO process. The initial discharges were preferred to start on β-Ti phases localized at the grain boundaries and then extends to the surrounding α-Ti grains. The presence of α- and β-Ti phases was also responsible for the different local coating surface morphology. A highly sintered morphology and larger-sized micro-pores developed firstly on the layer on β-Ti phases, with higher concentration of vanadium. These findings highlight the importance of microstructure of Ti6Al4V alloy on the formation of PEO coatings. Under the selected conditions of PEO processing, the higher current density promotes the growing of the coating and reduces the surface roughness of the resultant coating. The ex-situ characterization of the coatings after certain periods shows that the final coatings mainly consist of anatase, rutile and an amorphous phase containing phosphorous. The formation of rutile, transformed from anatase, is influenced by the effective temperature of the discharges, thus the ratio of anatase to rutile is decreasing with treatment time. The in-situ characterization of phase evolution showed the formation of an amorphous phase in parallel with an expanded α-Ti phase, which is a result of oxygen incorporation into solid solution into the titanium lattice. Interestingly, the main formation of crystalline phases occur only when the HV is turned off and the coating obviously cools down. %0 journal article %@ 2452-199X %A Wang, W.,Blawert, C.,Zan, R.,Sun, Y.,Peng, H.,Ni, J.,Han, P.,Suo, T.,Song, Y.,Zhang, S.,Zheludkevich, M.,Zhang, X. %D 2021 %J Bioactive Materials %N 12 %P 4333-4341 %R doi:10.1016/j.bioactmat.2021.04.020 %T A novel lean alloy of biodegradable Mg–2Zn with nanograins %U https://doi.org/10.1016/j.bioactmat.2021.04.020 12 %X Lean alloy (low alloyed) is beneficial for long-term sustainable development of metal materials. Creating a nanocrystalline microstructure is a desirable approach to improve biodegradability and mechanical properties of lean biomedical Mg alloy, but it is nearly impossible to realize. In the present study, the bulk nanocrystalline Mg alloy (average grain size: ~70 nm) was successfully obtained by hot rolling process of a lean Mg-2wt.%Zn (Z2) alloy and both high strength ((223 MPa (YS) and 260 MPa (UTS)) and good corrosion resistance (corrosion rate in vivo: 0.2 mm/year) could be achieved. The microstructure evolution during the rolling process was analyzed and discussed. Several factors including large strain, fine grains, strong basal texture, high temperature and Zn segregation conjointly provided the possibility for the activation of pyramidal slip to produce nanocrystals. This finding could provide a new development direction and field of application for lean biomedical Mg alloys. %0 journal article %@ 2213-9567 %A Chen, L.,Guo, C.,Blawert, C.,Yang, J.,Chen, D.,Wang, X.,Yu, Z.,Zheludkevich, M.,Li, W. %D 2021 %J Journal of Magnesium and Alloys %N 5 %P 1820-1833 %R doi:10.1016/j.jma.2021.07.002 %T Evaluation of the biodegradation product layer on Mg-1Zn alloy during dynamical strain %U https://doi.org/10.1016/j.jma.2021.07.002 5 %X Magnesium (Mg) alloys are attractive biodegradable implant materials. The degradation products on Mg alloys play a critical role in the stability of the interface between implant and surrounding tissue. In the present study, the effects of dynamic deformation on the interface layer of biomedical Mg-1Zn alloy were investigated using the constant extension rate tensile tests (CERT) coupled with electrochemical impedance spectroscopy (EIS). The deformation of the Mg-1Zn alloy had an adverse influence on the impedance of the surface degradation layer formed in simulated body fluid that only containing inorganic compounds. However, the surface degradation layer with improved corrosion resistance was obtained for the strained samples tested in protein-containing simulated body fluid. The spontaneous or enhanced adsorption of protein into the degradation product led to a flexible and stable hybrid anti-corrosive layer. A relationship between the dynamic deformation of Mg alloy and the impendence of the degradation layer was established, which demonstrates the necessity for in situ characterisation of the evolution of the surface layer under dynamic condition. %0 journal article %@ 0257-8972 %A Han, J.,Blawert, C.,Tang, S.,Yang, J.,Hu, J.,Zheludkevich, M. %D 2021 %J Surface and Coatings Technology %N %P 127030 %R doi:10.1016/j.surfcoat.2021.127030 %T Formation and corrosion behaviors of calcium phosphate coatings on plasma electrolytic oxidized Mg under changing chemical environment %U https://doi.org/10.1016/j.surfcoat.2021.127030 %X In order to form calcium phosphate (CaPh) coatings in the changing chemical environment, a drop wise addition procedure is performed during electro-deposition process. Two kind of electrolytes of KH2PO4 and K2HPO4, are added into Ca(NO3)2 solution respectively where plasma electrolytic oxidized (PEO) magnesium is placed. Results indicate that the phase composition and morphologies of the CaPh coatings are modified due to the changing chemical composition of electrolyte. Only calcium hydrogen phosphate dihydrate (DCPD) is formed on the PEO surface in the presence of KH2PO4 electrolyte, while a combination of hydroxyapatite (HA) and DCPD is obtained on the PEO surface in the electrolyte containing K2HPO4. The latter coating exhibits superior corrosion resistance in simulated body fluid, which implies the feasibility of the proposed strategy in fabricating biodegradable coating for Mg alloys. %0 journal article %@ 0925-8388 %A Han, J.,Luthringer, B.,Tang, S.,Hu, J.,Blawert, C.,Zheludkevich, M. %D 2021 %J Journal of Alloys and Compounds %N %P 160793 %R doi:10.1016/j.jallcom.2021.160793 %T Evolution and performance of a MgO/HA/DCPD gradient coating on pure magnesium %U https://doi.org/10.1016/j.jallcom.2021.160793 %X A composite calcium phosphate (CaPh) coating containing calcium hydrogen phosphate dihydrate (DCPD) and hydroxyapatite (HA) is fabricated on plasma electrolytic oxidized (PEO) magnesium via electro-assisted deposition. During immersion in simulated body fluid, the soluble DCPD stimulates the precipitation of HA and remains the degradability of the system, while the stable HA reinforces the corrosion resistance along with PEO layer. The morphology, thickness and corrosion property of the coating evolve remarkably with the deposition time. Various growth patterns of DCPD are presented in different period which noticeably influences the interfacial combination, as well as corrosion resistance. The composite coating after 60 min deposition shows most compact morphology and stable interfacial combination, leading to excellent corrosion resistance, apatite formation ability and cell attachment behavior. %0 journal article %@ 0300-9440 %A Hejjaj, C.,AitAghzzaf, A.,Scharnagl, N.,Zheludkevich, M.,Hakkou, R.,Fischer, C. %D 2021 %J Progress in Organic Coatings %N %P 106500 %R doi:10.1016/j.porgcoat.2021.106500 %T Introduction of an innovative corrosion-protective alkyd steel coating based on a novel layered aluminum tripolyphosphate loaded with 6-amino hexanoic acid (ATP-6-AHA) %U https://doi.org/10.1016/j.porgcoat.2021.106500 %X The novel hybrid phosphate pigment 6-amino hexanoic acid (6-AHA) intercalated in layered aluminum di-hydrogen tripolyphosphate (ATP-6-AHA) was successfully embedded in an alkyd coating at 5.0 wt% and applied on low carbon steel. Layered pigments used in coatings are becoming very attractive due to the improvement of the coatings barrier properties. The current study revealed superior corrosion protection of ATP-6-AHA coating on carbon steel with a polarization resistance of 1.3 108 Ohm·cm2 after three weeks immersed in a 3.5 wt% NaCl solution, using electrochemical impedance spectroscopy (EIS). The adhesion and surface roughness of coated samples were evaluated using pull of test and laser scanning microscopy. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to assess the corrosion protection of ATP-6-AHA alkyd coating. Results revealed a protective film on steel surface comprising iron phosphate. %0 journal article %@ 2238-7854 %A Neves, C.,Sousa, I.,Freitas, M.,Moreira, L.,Costa, C.,Teixeira, J.,Fraga, S.,Pinto, E.,Almeida, A.,Scharnagl, N.,Zheludkevich, M.,Ferreira, M.,Tedim, J. %D 2021 %J Journal of Materials Research and Technology : JMRT %N %P 1908-1922 %R doi:10.1016/j.jmrt.2021.05.090 %T Insights into corrosion behaviour of uncoated Mg alloys for biomedical applications in different aqueous media %U https://doi.org/10.1016/j.jmrt.2021.05.090 %X MgCa and MgGd series of alloys are often reported as promising candidates for biomedical applications. In the present study, cytotoxicity and corrosion behavior of Mg1Ca and Mg10Gd alloys in different electrolytes (NaCl, PBS, MEM) have been investigated in order to make a direct comparison and understand the mechanisms behind their performance. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were employed to analyze corrosion processes depending on media composition, whereas X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate crystalline structure, phase composition and surface morphology of the corroded substrates after immersion in the different electrolytes. Moreover, cytotoxicity of the Mg alloys was assessed using the WST-1 reduction and lactate dehydrogenase (LDH) release assays in L929 mouse fibroblasts. The electrochemical results showed that Mg1Ca has a lower degradation rate when compared to Mg10Gd, due to the lower microgalvanic effects and the presence of Ca as an alloying element. Furthermore, the corrosion activity is reduced in MEM, for both alloys, when compared to NaCl and PBS. The cytotoxicity assays revealed that Mg10Gd was cytotoxic in all the conditions tested, while the toxicity of Mg1Ca was low. Overall, these findings show that Mg1Ca alloy presents a higher corrosion resistance and biocompatibility and is a promising material to be used in biomedical implants. %0 journal article %@ 2405-8297 %A Deng, M.,Wang, L.,Vaghefinazari, B.,Xu, W.,Feiler, C.,Lamaka, S.,Höche, D.,Zheludkevich, M.,Snihirova, D. %D 2021 %J Energy Storage Materials %N %P 238-247 %R doi:10.1016/j.ensm.2021.09.008 %T High-energy and durable aqueous magnesium batteries: Recent advances and perspectives %U https://doi.org/10.1016/j.ensm.2021.09.008 %X Aqueous Mg batteries are promising energy storage and conversion systems to cope with the increasing demand for green, renewable and sustainable energy. Realization of high energy density and long endurance system is significant for fully delivering the huge potential of aqueous Mg batteries, which has drawn increasing attention and investigations from researchers worldwide in the last years. Herein, a thorough insight into recent progress in aqueous Mg battery system is presented in terms of anode development and electrolyte tailoring. Accordingly, potential directions to move in the future for battery advances are proposed. Concomitantly, prospective application of computational methods assisted by machine learning for battery performance boosting is discussed. Moreover, a comprehensive understanding on self-discharge of Mg anodes in aqueous electrolytes is given based on recently published results. Overcoming this problem paves the way for achieving high-capacity anodes and consequently high-energy batteries. %0 journal article %@ 0010-938X %A Vaghefinazari, B.,Wang, C.,Mercier, D.,Mei, D.,Seyeux, A.,Marcus, P.,Blawert, C.,Lamaka, S.V.,Zheludkevich, M.L. %D 2021 %J Corrosion Science %N %P 109830 %R doi:10.1016/j.corsci.2021.109830 %T Adverse effect of 2,5PDC corrosion inhibitor on PEO coated magnesium %U https://doi.org/10.1016/j.corsci.2021.109830 %X Besides their noteworthy tribological and corrosion protection properties, Plasma Electrolytic Oxidation (PEO) coatings feature a porous microstructure that is able to host corrosion inhibitors. This study reveals that although 2,5pyridindicarboxylate (2,5PDC) shows a remarkable corrosion inhibition effect for bare AZ21 Mg alloy, it can extensively deteriorate a PEO coating on the same Mg substrate, resulting in an overall accelerated failure of the PEO-coated AZ21 alloy. The deteriorative behavior of 2,5PDC towards PEO-coated AZ21 is explained based on the characterization of the bare and PEO-coated AZ21 exposed to the NaCl electrolyte with and without inhibitor using EIS, SEM, STEM and ToF-SIMS. %0 journal article %@ 0010-938X %A Yasakau, K.A.,Bastos, A.C.,Haffner, D.,Quandt, E.,Feyerabend, F.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2021 %J Corrosion Science %N %P 109590 %R doi:10.1016/j.corsci.2021.109590 %T Sacrificial protection of Mg-based resorbable implant alloy by magnetron sputtered Mg5Gd alloy coating: A short-term study %U https://doi.org/10.1016/j.corsci.2021.109590 %X In this work metallic pins made of Mg5Gd alloy were coated with magnetron sputtered PVD Mg5Gd layers. Immersion tests in Hank’s balanced salt solution (HBSS) were performed. The PVD coating drastically reduced the corrosion rate of the Mg5Gd pin. The corrosion mechanism of the coating was studied in model electrochemical measurements by Scanning Vibrating Electrode Technique and galvanic current measurements. The tests revealed the preferential anodic dissolution of the Mg5Gd coating galvanically coupled with the bulk Mg5Gd pin. Local measurements of Volta potential difference revealed the VPD contrast between the pin and the coating surfaces only after immersion in HBSS. %0 journal article %@ 0010-938X %A Mei, D.,Wang, C.,Nienaber, M.,Pacheco, M.,Barros, A.,Neves, S.,Reis, R.,Zhu, S.,Bohlen, J.,Letzig, D.,Guan, S.,Zheludkevich, M.,Lamaka, S. %D 2021 %J Corrosion Science %N %P 109567 %R doi:10.1016/j.corsci.2021.109567 %T Corrosion behavior of Mg wires for ureteral stent in artificial urine solution %U https://doi.org/10.1016/j.corsci.2021.109567 %X Ureteral stents are a relatively new potential application for biodegradable Mg alloys. In this study, the corrosion behavior of Mg-1Zn wires and pure Mg wires in artificial urine solution (AUS) is investigated. It is found that AUS possesses a strong pH buffer effect. Hydrogen evolution measurement cannot be used for Mg corrosion test in this AUS due to the oxygen scavenging effect of sulfite, which is a component of AUS. The corrosion products consist of two layers, MgNH4PO4·6H2O and Mg(OH)2. The partially protective MgNH4PO4·6H2O slows down the Mg corrosion, but it indicates the encrustation risk on bare Mg-based ureteral stents. %0 journal article %@ 2057-3960 %A Schiessler, E.,Würger, T.,Lamaka, S.,Meißner, R.,Cyron, C.,Zheludkevich, M.,Feiler, C.,Aydin, R. %D 2021 %J npj Computational Materials %N 1 %P 193 %R doi:10.1038/s41524-021-00658-7 %T Predicting the inhibition efficiencies of magnesium dissolution modulators using sparse machine learning models %U https://doi.org/10.1038/s41524-021-00658-7 1 %X The degradation behaviour of magnesium and its alloys can be tuned by small organic molecules. However, an automatic identification of effective organic additives within the vast chemical space of potential compounds needs sophisticated tools. Herein, we propose two systematic approaches of sparse feature selection for identifying molecular descriptors that are most relevant for the corrosion inhibition efficiency of chemical compounds. One is based on the classical statistical tool of analysis of variance, the other one based on random forests. We demonstrate how both can—when combined with deep neural networks—help to predict the corrosion inhibition efficiencies of chemical compounds for the magnesium alloy ZE41. In particular, we demonstrate that this framework outperforms predictions relying on a random selection of molecular descriptors. Finally, we point out how autoencoders could be used in the future to enable even more accurate automated predictions of corrosion inhibition efficiencies. %0 journal article %@ 0372-2929 %A Gnedenkov, A.,Lamaka, S.,Sinebryuhov, S.,Filonina, V.,Zheludkevich, M.,Gnedenkov, S. %D 2021 %J Tsvetnye Metally %N 12 %P 47-52 %R doi:10.17580/tsm.2021.12.07 %T Localized corrosion of magnesium alloys potentially applicable for medical implants: fundamental aspects %U https://doi.org/10.17580/tsm.2021.12.07 12 %X A comparative analysis of the corrosion activity of bioresorbable MA8 magnesium alloy (Mg– Mn – Ce system) in a medium for cultivation of mammalian cells (minimum essential medium, MEM) and 0.83 wt. % aqueous NaCl solution was performed. The development of the corrosion process on the surface of a magnesium alloy in two media was established using local scanning electrochemical methods (scanning vibrating electrode technique and scanning ion-selective electrode technique), traditional electrochemical methods (potentiodynamic polarization, electrochemical impedance spectroscopy) and hydrogen evolution measurements. The protective properties of the corrosion film formed on the alloy in MEM, as well as during exposure to NaCl solution, were established. The composition of the layer of corrosion products formed on the magnesium alloy in MEM was studied using confocal Raman spectroscopy, X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-Ray analysis. Calcium-phosphate compounds are the main products formed on the surface of a magnesium alloy during immersion in MEM. The model of corrosion mechanism of magnesium alloy in MEM, which includes three stages of the development of surface film, is proposed. The formation on the magnesium alloy in MEM of corrosion product layer, including magnesium-substituted hydroxyapatite, stabilizes the local pH below 9.0, which along with the presence of organic acids, does not allow increasing the pH during corrosion. A diagram that allows one to determine the possible reactions occurring on the surface of a magnesium alloy in MEM and the thermodynamic probability of the formation of chemical compounds based on the values of the local pH is designed. The obtained results indicate the prospect of using bioresorbable magnesium implants in surgery. %0 journal article %@ 1003-6326 %A Davoodi, F.,Atapour, M.,Blawert, C.,Zheludkevich, M. %D 2021 %J Transactions of Nonferrous Metals Society of China %N 12 %P 3719-3738 %R doi:10.1016/S1003-6326(21)65759-X %T Wear and corrosion behavior of clay containing coating on AM 50 magnesium alloy produced by aluminate-based plasma electrolytic oxidation %U https://doi.org/10.1016/S1003-6326(21)65759-X 12 %X This study aims to examine the effect of clay micro particles addition on the microstructure, wear and corrosion behavior of PEO coatings on AM 50 magnesium alloy. PEO coatings were prepared using an aluminate-based electrolyte with and without the presence of 5 g/L clay particles. The structure and composition of the coatings were evaluated using SEM, EDS and XRD. The wear investigations were conducted using a ball-on-disk tribometer at 2, 5 and 10 N loads. The corrosion behavior of the coatings was examined using polarization and EIS tests in 0.5 wt.%NaCl. The results revealed that the addition of clay particles deteriorated the wear resistance of the coatings under the loads of 5 and 10 N. The SEM examinations of the worn surfaces indicated that a combination of adhesive and abrasive wear mechanisms was activated for the coating with clay particles. The poor wear performance of the clay-incorporated coating was related to its lower adhesion strength and higher roughness. The potentiodynamic polarization examinations revealed that the addition of clay particles slightly decreased the corrosion rate of the coatings. Corrosion resistance of the clay-containing coating was attributed to its compactness, as indicated by the results of EIS tests. %0 journal article %@ 1944-8244 %A Zhang, Y.,Wang, J.,Zhao, S.,Serdechnova, M.,Blawert, C.,Wang, H.,Zheludkevich, M.,Chen, F. %D 2021 %J ACS Applied Materials and Interfaces %N 43 %P 51685-51694 %R doi:10.1021/acsami.1c13738 %T Double-Ligand Strategy to Construct an Inhibitor-Loaded Zn-MOF and Its Corrosion Protection Ability for Aluminum Alloy 2A12 %U https://doi.org/10.1021/acsami.1c13738 43 %X A promising double-ligand strategy for the delivery of active corrosion inhibitors by a Zn(II)-based metal–organic framework (Zn-MOF) is developed. Zn-MOF compounds were synthesized by a facile one-pot solvothermal method and characterized. The Zn-MOF is based on the corrosion inhibitor benzotriazole (BTA) and 2,5-furandicarboxylic acid (H2FDA) ligand, which is a promising renewable building block alternative to terephthalic or isophthalic acid. The crystal structure and morphology are characterized by single-crystal X-ray diffraction analysis, powder X-ray diffraction analysis (PXRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The synthesized MOF crystallites are in the trigonal space group R3c with the cell parameters in a three-dimensional (3D) anionic framework. Their ability to inhibit the corrosion process of aluminum alloy 2A12 in NaCl solution was also evaluated by immersion tests in solutions with and without a MOF. The postcorrosion analysis was performed by SEM and X-ray photoelectron spectroscopy (XPS). Additional information about the inhibition efficiency was obtained by electrochemical impedance spectroscopy (EIS). The results suggest that the as-synthesized MOF can release the inhibitors and form protective layers effectively on the surface of the aluminum alloy. The use of inhibitor-loaded MOF nanocontainers provides promising opportunities for the smart delivery of inhibitors and effective corrosion protection of 2A12 aluminum alloys. %0 journal article %@ 0378-7753 %A Deng, M.,Wang, L.,Höche, D.,Lamaka, S.,Jiang, P.,Snihirova, D.,Scharnagl, N.,Zheludkevich, M. %D 2020 %J Journal of Power Sources %N %P 228528 %R doi:10.1016/j.jpowsour.2020.228528 %T Ca/In micro alloying as a novel strategy to simultaneously enhance power and energy density of primary Mg-air batteries from anode aspect %U https://doi.org/10.1016/j.jpowsour.2020.228528 %X Herein we report micro-alloying with the combination of Ca/In as a novel strategy to improve the anode performance for Mg-air batteries. Two micro-alloyed Mg–Ca–In anodes, i.e. Mg−0.1%Ca−0.2%In and Mg−0.2%Ca−0.4%In (wt%), are fabricated and evaluated in both configurations: half-cell and Mg-air full cell. Re-deposition of metallic In on anode surface during discharge is demonstrated. Anodic activation is then promoted by galvanic coupling between Mg and the re-deposited In, and film breakdown induced by In re-precipitation at the substrate/oxide film interface. Thus, the voltage and power density of Mg-air system are enhanced via adopting Mg–Ca–In anodes. Besides, wasteful-discharge of the Ca/In micro-alloyed anodes, which is related to the negative difference effect (NDE), is significantly suppressed. Anodic efficiency is consequently improved, reaching 80.2% at 5 mA cm−2 initial current density, and so is the service life of the Mg-air battery. Due to the enhanced voltage and anodic efficiency, Mg–Ca–In anodes enable Mg-air battery to exhibit outstanding energy density, e.g. 2259 Wh kg−1 at 5 mA cm−2. Mg−0.1%Ca−0.2%In anode possesses superior performance in terms of low wasteful-discharge, enhanced discharge activity and high anodic efficiency. Therefore, we recommend micro-alloyed Mg–Ca–In, like Mg−0.1%Ca−0.2%In, as excellent candidates for anode materials of primary aqueous Mg-air batteries. %0 journal article %@ 0010-938X %A Deng, M.,Wang, L.,Höche, D.,Lamaka, S.,Snihirova, D.,Jiang, P.,Zheludkevich, M. %D 2020 %J Corrosion Science %N %P 108958 %R doi:10.1016/j.corsci.2020.108958 %T Corrosion and discharge properties of Ca/Ge micro-alloyed Mg anodes for primary aqueous Mg batteries %U https://doi.org/10.1016/j.corsci.2020.108958 %X Ge is evaluated as a micro-alloying element for newly-developed Mg-Ca anodes. The combination of Ca/Ge is effective for suppressing cathodic HER kinetics, resulting in highly negative OCP and a low corrosion rate (0.2 mm y–1). For air battery, Mg-0.1 %Ca-0.1 %Ge (wt%) anode exhibits similar voltage to Mg-0.1 %Ca in NaCl solution, but the highly negative OCP enables it with enhanced voltage in salicylate-containing electrolyte (1.7 V at 1 mA cm–2 versus 1.63 V of Mg-0.1 %Ca). Beside, all micro-alloyed Mg-Ca, Mg-Ge and Mg-Ca-Ge anodes show similar self-discharge rates and high utilization efficiency (∼60 % at 10 mA cm–2). %0 journal article %@ 0378-7753 %A Wang, L.,Snihirova, D.,Deng, M.,Vaghefinazari, B.,Lamaka, S.,Höche, D.,Zheludkevich, M. %D 2020 %J Journal of Power Sources %N %P 228106 %R doi:10.1016/j.jpowsour.2020.228106 %T Tailoring electrolyte additives for controlled Mg-Ca anode activity in aqueous Mg-air batteries %U https://doi.org/10.1016/j.jpowsour.2020.228106 %X Aqueous primary Mg-air batteries exhibit many merits as potential energy storage and conversion devices. In this work, the discharge performance of water based Mg-air batteries with advanced Mg-Ca anode was boosted by adding Mg2+ complexing agents into the electrolyte. The effect of electrolyte additives on the corrosion behavior and discharge properties of micro-alloyed Mg-Ca anode was investigated via hydrogen evolution test and half-cell discharge test. Electrochemical impedance spectroscopy (EIS) was performed to evaluate the effect of different electrolyte additives on the discharge activity of Mg-Ca anode. Basic characteristics of aqueous Mg-air battery in selected additive solution were tested and compared to pure NaCl solution. The results show that the addition of dedicated Mg2+ complexing agents can efficiently increase the discharge voltage and specific energy of respective Mg-air batteries. At 0.5 mA cm−2, the discharge voltage reaches 1.86 V with regard to the cell containing 0.1 M 5-Sulfosalicylate, which is 270 mV higher than the discharge voltage in bulk 3.5 wt % NaCl. The highest specific energy for the tested system is above 3.0 kWh kg−1 in NaCl solution with 0.1 M citrate at 1 mA cm−2 discharge current density. %0 journal article %@ 1005-0302 %A Jiang, P.,Blawert, C.,Bohlen, J.,Zheludkevich, M. %D 2020 %J Journal of Materials Science & Technology %N %P 107-116 %R doi:10.1016/j.jmst.2020.04.042 %T Corrosion performance, corrosion fatigue behavior and mechanical integrity of an extruded Mg4Zn0.2Sn alloy %U https://doi.org/10.1016/j.jmst.2020.04.042 %X Magnesium alloys are promising as load bearing components. They are inevitably exposed to cyclic loading and corrosive environment in actual service, which can consequently result in corrosion fatigue failure and loss of mechanical integrity of the material. Therefore, in the present study, the corrosion behavior, corrosion fatigue performance and mechanical integrity of an extruded Mg4Zn0.2Sn (wt.%) alloy were thoroughly studied in two corrosive electrolytes. Strong localized corrosion occurred when the alloy was immersed in deionized water based sodium chloride (NaCl) solution. The poor corrosion resistance of the alloy resulted in a fast deterioration of the tensile properties after pre-exposure to salt spray and a poor fatigue resistance in deionized water based NaCl solution. In comparison, the active dissolution of the substrate was sufficiently suppressed in artificial tap water based NaCl solution due to the formation of highly protective corrosion product layers. This consequently conferred longer fatigue life on the alloy in the electrolyte. Our results emphasized the influence of corrosion on the fatigue behavior and tensile properties of magnesium alloys. %0 journal article %@ 0010-938X %A Korrapati, V.,Scharnagl, N.,Letzig, D.,Zheludkevich, M. %D 2020 %J Corrosion Science %N %P 108619 %R doi:10.1016/j.corsci.2020.108619 %T Self-assembled layers for the temporary corrosion protection of magnesium-AZ31 alloy %U https://doi.org/10.1016/j.corsci.2020.108619 %X Self-assembled (SA) layers of phosphates/silanes/thiols were applied as temporary protective films on Mg-AZ31. Retention of phosphoryl oxygen (Pdouble bondO) on magnesium (Mg), demonstrates dominant bidentate bonding. Distribution of the phosphate nodules are homogeneous, while silanes form island/cluster depositions, apparently sealing the pores and stabilizing the oxide of Mg. Cathodic prepolarization testifies that alkalinization can cause an additional conversion of the SA layers, increasing its protective properties. Although phosphates are with low corrosion rates, hexadecyltrimethoxysilane exhibits high corrosion impedance due to multilayer distribution. The barrier properties are better concluded by considering the resistance (Rct and R(oxi + SA)) values of impedance measurements. %0 journal article %@ 2397-2106 %A Wang, C.,Mei, D.,Wiese, G.,Wang, L.,Deng, M.,Lamaka, S.,Zheludkevich, M. %D 2020 %J npj Materials Degradation %N %P 42 %R doi:10.1038/s41529-020-00146-1 %T High rate oxygen reduction reaction during corrosion of ultra-high-purity magnesium %U https://doi.org/10.1038/s41529-020-00146-1 %X Comprehending the corrosion mechanism of magnesium is of major interest in diverse fields. Typically, hydrogen evolution reaction is considered as the only cathodic reaction during Mg corrosion. However, recent works demonstrate importance of considering oxygen reduction reaction (ORR) as a second cathodic process at specific conditions. With oxygen micro-optode, we show that ORR rate was higher on slower corroding ultra-high-purity Mg (UHP-Mg), while lower on faster corroding commercially pure Mg (CP-Mg), where massive hydroxide layer impeded oxygen permeation. These findings shed light on yet another facet of complex mechanism of Mg corrosion. %0 journal article %@ 2045-2322 %A Würger, T.,Feiler, C.,Vonbun-Feldbauer, G.,Zheludkevich, M.,Meißner, R. %D 2020 %J Scientific Reports %N %P 15006 %R doi:10.1038/s41598-020-71694-4 %T A first-principles analysis of the charge transfer in magnesium corrosion %U https://doi.org/10.1038/s41598-020-71694-4 %X Magnesium is the lightest structural engineering material and bears high potential to manufacture automotive components, medical implants and energy storage systems. However, the practical use of untreated magnesium alloys is restricted as they are prone to corrosion. An essential prerequisite for the control or prevention of the degradation process is a deeper understanding of the underlying corrosion mechanisms. Prior investigations of the formation of gaseous hydrogen during the corrosion of magnesium indicated that the predominant mechanism for this process follows the Volmer–Heyrovský rather than the previously assumed Volmer–Tafel pathway. However, the energetic and electronic states of both reaction paths as well as the charge state of dissolved magnesium have not been fully unraveled yet. In this study, density functional theory calculations were employed to determine these parameters for the Volmer, Tafel and Heyrovský steps to gain a comprehensive understanding of the major corrosion mechanisms responsible for the degradation of magnesium. %0 journal article %@ 0257-8972 %A Nguyen, T.,Nguyen, A.,Tran, B.,Vu, K.,Tran, D.,Phan, T.,Scharnagl, N.,Zheludkevich, M.,To, T. %D 2020 %J Surface and Coatings Technology %N %P 126165 %R doi:10.1016/j.surfcoat.2020.126165 %T Molybdate intercalated hydrotalcite/graphene oxide composite as corrosion inhibitor for carbon steel %U https://doi.org/10.1016/j.surfcoat.2020.126165 %X Molybdate intercalated hydrotalcite/graphene oxide composite (HT-MoO4/GO) as corrosion inhibitor for carbon steel was synthesized and characterized. The influence of HT-MoO4/GO on corrosion resistance of waterborne epoxy coating applied on carbon steel was investigated. The results showed that hydrotalcite containing molybdate was formed on GO surface and the molybdate content in HT-MoO4/GO was 15.3%. HT-MoO4/GO provided both anodic and cathodic inhibition effects for carbon steel with an efficiency of 96%. The corrosion inhibition of HT-MoO4/GO depended not only on the inhibition effect of released molybdate but also on the deposition of HT-MoO4/GO particles on the steel surface. HT-MoO4/GO at 1 wt% concentration improved corrosion resistance of waterborne epoxy coatings. The presence of GO increased the effects of HT-MoO4 on protection properties of waterborne epoxy coatings. %0 journal article %@ 0169-4332 %A Chen, Y.,Lu, X.,Lamaka, S.,Ju, P.,Blawert, C.,Zhang, T.,Wang, F.,Zheludkevich, M. %D 2020 %J Applied Surface Science %N %P 144462 %R doi:10.1016/j.apsusc.2019.144462 %T Active protection of Mg alloy by composite PEO coating loaded with corrosion inhibitors %U https://doi.org/10.1016/j.apsusc.2019.144462 %X A PEO (Plasma Electrolytic Oxidation) /Sol-gel composite coating was prepared on AZ91 magnesium alloy. The porous layer produced by PEO was loaded with corrosion inhibitors (sodium salts of glycolic, 4-aminosalicylic and 2,6-pyridinedicarboxylic acids). Sealed with a thin sol-gel layer, this sandwich-like structure demonstrated durable barrier and active corrosion protection as shown by electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The active protection mechanism ensures self-healing ability of the coating system, which was obtained by suppression of the re-deposition of impurity and/or adsorption of the impregnated inhibitors upon the exposed surface. %0 journal article %@ 1001-0521 %A Liu, W.,Liu, Y.,Blawert, C.,Zheludkevich, M.,Fan, C.,Talha, M.,Lin, Y. %D 2020 %J Rare Metals %N 12 %P 1425-1439 %R doi:10.1007/s12598-020-01523-0 %T Microstructure, wear and corrosion performance of plasma electrolytic oxidation coatings formed on D16T Al alloy %U https://doi.org/10.1007/s12598-020-01523-0 12 %X The plasma electrolytic oxidation (PEO) coatings were produced on D16T Al alloy in the aluminate and silicate electrolyte with and without graphene. The phase composition, microstructure and elemental distribution of the coatings were tested by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). The wear and corrosion resistance of PEO coatings were evaluated by dry sliding wear tests and electrochemical impedance spectroscopy (EIS). The morphology feature of the wear tracks was compared and analyzed by SEM and three-dimensional microscope. The results demonstrate that the structure, wear and corrosion resistance of PEO coatings with graphene are better than that of PEO coatings without graphene. The coating fabricated in the aluminate electrolyte with graphene exhibited the lowest roughness. The coated samples formed in silicate electrolyte with graphene displayed the thickest, densest and the most compact coating. It exhibited the best wear and corrosion resistance due to the incorporation mode of graphene in the coatings. The mechanism of graphene improving the wear and corrosion resistance of PEO coating was further discussed. In summary, the comprehensive performances of PEO coatings formed in silicate electrolyte on D16T Al alloy are superior to that produced in aluminate electrolyte. %0 journal article %@ 1005-0302 %A Wu, T.,Blawert, C.,Zheludkevich, M. %D 2020 %J Journal of Materials Science & Technology %N %P 75-85 %R doi:10.1016/j.jmst.2019.12.031 %T Influence of secondary phases of AlSi9Cu3 alloy on the plasma electrolytic oxidation coating formation process %U https://doi.org/10.1016/j.jmst.2019.12.031 %X To understand the formation and growth of plasma electrolytic oxidation (PEO) coatings in presence of different secondary phases in a substrate, PEO treatment was carried out on AlSi9Cu3 alloy at different treatment times ranging from 15 s to 480 s. The coating formation and evolution process was traced by surface and cross-sectional observation of the layers on the different phases of the alloy. The results demonstrated a sequential involvement of the different phases in the plasma discharges: firstly, discharges start on the α-Al matrix, then on the intermetallic Al2Cu and β-Al5FeSi phases at the same time and finally on the eutectic Si. The presence of intermetallic Al2Cu remarkably affects the initial dissolution, the deposition of conversion products and the ignition of discharges at the early stages of processing. Eutectic Si in the substrate exhibits the highest electrochemical stability at all stages and contributes in the beginning to a distinct coating morphology eventually. The resultant PEO coating tends to be uniform if processing times are longer and a double-layer structure appears in the coating. %0 journal article %@ 0010-938X %A Gnedenkov, A.,Lamaka, S.,Sinebryukhov, S.,Mashtalyar, D.,Egorkin, V.,Imshinetskiy, I.,Zavidnaya, A.,Zheludkevich, M.,Gnedenkov, S. %D 2020 %J Corrosion Science %N %P 108552 %R doi:10.1016/j.corsci.2020.108552 %T Electrochemical behaviour of the MA8 Mg alloy in minimum essential medium %U https://doi.org/10.1016/j.corsci.2020.108552 %X The difference of the protective properties of the corrosion film formed on the MA8 Mg alloy in the mammalian cell culture medium (MEM) and 0.83 wt. % NaCl solution is established using OCP, PDP and EIS tests. The impedance modulus in the frequency range from 105 Hz down to 10−1 Hz for the sample immersed in MEM is higher than that for the sample immersed in NaCl solution. Ca and P rich deposits are formed in the corrosion layer on the Mg alloy in MEM. The model of the corrosion mechanism for MA8 Mg alloy in the MEM is proposed. %0 journal article %@ 0010-938X %A Gnedenkov, A.,Mei, D.,Lamaka, S.,Sinebryukhov, S.,Mashtalyar, D.,Vyaliy, I.,Zheludkevich, M.,Gnedenkov, S. %D 2020 %J Corrosion Science %N %P 108689 %R doi:10.1016/j.corsci.2020.108689 %T Localized currents and pH distribution studied during corrosion of MA8 Mg alloy in the cell culture medium %U https://doi.org/10.1016/j.corsci.2020.108689 %X Electrochemical behaviour of MA8 magnesium alloy in minimum essential medium (MEM) and 0.83 wt. % NaCl solution is compared using SVET, local pH measurements and hydrogen evolution tests. Corrosion products formed on the alloy surfaces are characterized using XRD and SEM-EDX analysis. Potential by-products of cells and bacteria activities increase the sample activity in MEM at the initial stage of material immersion. Hydrogen evolution rate is higher for samples in NaCl solution in comparison with MEM. Formation of partially protective magnesium-substituted hydroxyapatite stabilizes the local pH of MEM below 9.0 and does not allow to increase the pH during corrosion. %0 journal article %@ 0010-938X %A Maltseva, A.,Lamaka, S.,Yasakau, K.,Mei, D.,Kurchavov, D.,Zheludkevich, M.,Lefevre, G.,Volovitch, P. %D 2020 %J Corrosion Science %N %P 108484 %R doi:10.1016/j.corsci.2020.108484 %T In situ surface film evolution during Mg aqueous corrosion in presence of selected carboxylates %U https://doi.org/10.1016/j.corsci.2020.108484 %X Mechanisms of inhibition of Mg aqueous corrosion in presence of chloride by sodium salicylate (Sal), 2,5-pyridinedicarboxylate (PDC) and fumarate (Fum) were studied by in situ Raman spectroscopy, ATR-FTIR, GD-OES and hydrogen collection. In situ detected surface films were composed by Mg(OH)2 nano-crystals and included inhibitors. All carboxylates significantly modified Mg(OH)2 growth kinetics as well as pevented chloride incorporation in the film. Vibrational spectra of the surface films demonstrated specific interactions between the carboxylates and the surface: adsorption of Sal and Fum on the oxide/hydroxide, precipitation of coordination polymer by PDC, dissolution of iron inclusions via formation of iron-Sal soluble complexes. %0 journal article %@ 0010-938X %A Chen, L.,Blawert, C.,Yang, J.,Hou, R.,Wang, X.,Zheludkevich, M.,Lia, W. %D 2020 %J Corrosion Science %N %P 108876 %R doi:10.1016/j.corsci.2020.108876 %T The stress corrosion cracking behaviour of biomedical Mg-1Zn alloy in synthetic or natural biological media %U https://doi.org/10.1016/j.corsci.2020.108876 %X In the present study, the effects of degradation environment on the in vitro stress corrosion cracking (SCC) behaviour of biomedical Mg-1Zn alloy were investigated. The resistance to SCC’s initiation and propagation for Mg-1Zn alloy in synthetic cell culture medium and natural bovine calf serum (BCS) were improved compared to phosphate-buffered saline (PBS) and modified simulated body fluid (m-SBF), due to the homogenous corrosion and spontaneous adsorption of organic components. The elongation to failure obtained in BCS was reduced by around 30 % compared with that of the sample tested in air, indicating still a good ductility for Mg alloy. %0 journal article %@ 0257-8972 %A Pulido-González, N.,Torres, B.,Zheludkevich, M.,Rams, J. %D 2020 %J Surface and Coatings Technology %N %P 126314 %R doi:10.1016/j.surfcoat.2020.126314 %T High Power Diode Laser (HPDL) surface treatments to improve the mechanical properties and the corrosion behaviour of Mg-Zn-Ca alloys for biodegradable implants %U https://doi.org/10.1016/j.surfcoat.2020.126314 %X Biodegradability, low density and mechanical properties close to those of the bone are some of the intrinsic properties of the Mg-Zn-Ca alloys that have attracted significant attention for developing biodegradable implants. However, rapid degradation constitutes the main disadvantage of these alloys. In this work, two different alloys, Mg-1Zn-1Ca and Mg-3Zn-0.4Ca, were laser surface treated using a HPDL to increase hardness and to improve the corrosion performance. Depending on the laser parameters, a complete laser surface melting (LSM) or a selective laser surface melting (SLSM) were reached. The microstructure, mechanical properties and corrosion behaviour were established and compared. Higher laser input energies led to larger treated zones and in these cases two different regions could be distinguished: the outer zone, where the LSM took place, presented a more refined microstructure with a greater dispersion of secondary phases; the following zone suffered SLSM, in it only the secondary phases were modified by the HPDL. Hardness was 24%–27% higher than that of the untreated samples. The HPDL also reduced the corrosion rate by 21% and 37% for the Mg-1Zn-1Ca alloy and the Mg-3Zn-0.4Ca alloy, respectively, after 336 h of immersion in Hanks' solution at 37 °C. %0 journal article %@ 2352-9407 %A Bouali, A.,Serdechnova, M.,Blawert, C.,Tedim, J.,Ferreira, M.,Zheludkevich, M. %D 2020 %J Applied Materials Today %N %P 100857 %R doi:10.1016/j.apmt.2020.100857 %T Layered double hydroxides (LDHs) as functional materials for the corrosion protection of aluminum alloys: A review %U https://doi.org/10.1016/j.apmt.2020.100857 %X The search for new alternatives to replace chromate-based coatings is a matter of great importance. Since their official ban due to the raised concerns of hexavalent chromium to the human health and the environment, significant efforts have been devoted to finding a more suitable alternative for the corrosion protection of aluminum alloys. However, the task has been quite challenging since the potential replacement needs to fulfill several requirements both in terms of cost and exceptional corrosion performance. Layered double hydroxides (LDHs) have generated a lot of interest in the past few years. They have been proposed as prospective candidates to replace chromate based protective systems. The particular structure of LDH nanocontainers allows them to intercalate a number of corrosion inhibitors and release them on demand under the action of corrosion relevant triggers. Moreover, their flexible use as pigments in paints or as a pre-treatment directly as conversion layers makes their implementation even more convenient. This review presents a critical view to the studies performed till today on LDHs for corrosion protection of aluminum alloys. %0 journal article %@ 2045-2322 %A Petrova, E.,Serdechnova, M.,Shulha, T.,Lamaka, S.,Wieland, D.,Karlova, P.,Blawert, C.,Starykevich, M.,Zheludkevich, M. %D 2020 %J Scientific Reports %N 1 %P 8645 %R doi:10.1038/s41598-020-65396-0 %T Use of synergistic mixture of chelating agents for in situ LDH growth on the surface of PEO-treated AZ91 %U https://doi.org/10.1038/s41598-020-65396-0 1 %X The principal possibility to grow layered double hydroxide (LDH) at ambient pressure on plasma electrolytic oxidation (PEO) treated magnesium alloy AZ91 in the presence of chelating agents is demonstrated for the first time. It avoids hydrothermal autoclave conditions, which strongly limit wide industrial application of such coating systems, and the presence of carbonate ions in the electrolyte, which lead to the formation of “passive” non-functionalizable LDH. A combination of chelating agents (sodium diethylenetriamine-pentaacetate (DTPA) and salicylate) were introduced to the treatment solution. The role of each additive and the influence of treatment bath composition on the LDH formation processes are discussed. A synergistic effect of DTPA and salicylate during LDH formation is discovered and its possible explanation is proposed. %0 journal article %@ 0010-938X %A Feiler, C.,Mei, D.,Vaghefinazari, B.,Würger, T.,Meißner, R.H.,Luthringer-Feyerabend, B.J.C.,Winkler, D.A.,Zheludkevich, M.L.,Lamaka, S.V. %D 2020 %J Corrosion Science %N %P 108245 %R doi:10.1016/j.corsci.2019.108245 %T In silico screening of modulators of magnesium dissolution %U https://doi.org/10.1016/j.corsci.2019.108245 %X The vast number of small molecules with potentially useful dissolution modulating properties (inhibitors or accelerators) renders currently used experimental discovery methods time- and resource-consuming. Fortunately, emerging computer-assisted methods can explore large areas of chemical space with less effort. Here we show how density functional theory calculations and machine learning methods can work synergistically to generate robust and predictive models that recapitulate experimentally-derived corrosion inhibition efficiencies of small organic compounds for pure magnesium. We further validate our methods by predicting a priori the corrosion modulation properties of seven hitherto untested small molecules and confirm the prediction in subsequent experiments. %0 journal article %@ 1948-7185 %A Snihirova, D.,Wang, L.,Lamaka, S.,Wang, C.,Deng, M.,Vaghefinazari, B.,Höche, D.,Zheludkevich, M. %D 2020 %J The Journal of Physical Chemistry Letters %N 20 %P 8790-8798 %R doi:10.1021/acs.jpclett.0c02174 %T Synergistic Mixture of Electrolyte Additives: A Route to a High-Efficiency Mg–Air Battery %U https://doi.org/10.1021/acs.jpclett.0c02174 20 %X Magnesium primary cells are currently experiencing a renaissance following the suggestion of new strategies to boost their performance. The strategies suggested will maintain utilization efficiencies of 30–70%, which is considered to be relatively modest. In this work, the highest ever reported level of utilization efficiency of 82% is achieved for a Mg-based primary cell using a synergistic combination of electrolyte additives. It is demonstrated that the joint use of sodium nitrate and salicylate as electrolyte additives allows us to reach the aforementioned utilization efficiency of 5 mA/cm2 via offering an effective suppression of anode self-corrosion and uniform Mg dissolution under discharge conditions. %0 journal article %@ 0261-3069 %A Jiang, P.,Blawert, C.,Hou, R.,Bohlen, J.,Konchakova, N.,Zheludkevich, M.L. %D 2020 %J Materials and Design %N %P 108285 %R doi:10.1016/j.matdes.2019.108285 %T A comprehensive comparison of the corrosion performance, fatigue behavior and mechanical properties of micro-alloyed MgZnCa and MgZnGe alloys %U https://doi.org/10.1016/j.matdes.2019.108285 %X The fast and non-uniform corrosion of Mg alloys largely limits their practical applications in various fields. In present study, micro-alloyed extruded Mg0.5Zn0.2Ca and Mg0.5Zn0.2Ge alloys were developed to avoid the severe galvanic corrosion between Mg matrix and second phases. Corrosion behavior, mechanical integrity and fatigue behavior in two corrosive electrolytes of these two alloys were investigated. The results revealed a better short-term corrosion property for Mg0.5Zn0.2Ge alloy, but an improved long-term corrosion resistance for Mg0.5Zn0.2Ca alloy, resulting from the different protective abilities of surface layers and microstructures of the alloys. Although Mg0.5Zn0.2Ca alloy presented relatively lower strength owing to the weaker texture, it owned better mechanical integrity than Mg0.5Zn0.2Ge alloy due to the more uniform corrosion in salt spray, indicating the significant effect of localized corrosion on mechanical integrity of materials. Furthermore, the corrosion of the alloys in electrolytes decreased the fatigue resistance for both alloys, but Mg0.5Zn0.2Ca showed higher sensitivity to corrosive environments under cyclic loading. The comprehensive studies of these two alloys highlight the interactions between corrosion and mechanical integrity and/or fatigue behavior of materials and suggest the importance of the investigation of the overall properties when new Mg alloys are developed and evaluated for practical applications. %0 journal article %@ 0169-4332 %A Blawert, C.,Karpushenkov, S.A.,Serdechnova, M.,Karpushenkava, L.S.,Zheludkevich, M.L. %D 2020 %J Applied Surface Science %N %P 144552 %R doi:10.1016/j.apsusc.2019.144552 %T Plasma electrolytic oxidation of zinc alloy in a phosphate-aluminate electrolyte %U https://doi.org/10.1016/j.apsusc.2019.144552 %X In the frame of this work, plasma electrolytic oxidation of a zinc alloy was performed in a phosphate-aluminate electrolyte as a first approach. Phase composition and microstructure of the formed PEO coating was analysed as a function of treatment time and applied current density. The coatings are mainly composed out of ZnAl2O4 and ZnO with some smaller amounts of AlPO4 and Zn2P2O7. The coating formation starts with ZnO at lower discharge energies and changes to the reactive formation of ZnAl2O4 when the discharge energy is increasing. The phase composition is only influenced by the final voltage and not by the current density. Latter is only determining the growth rate of the coating. However, stresses in the coatings are high and the layers are cracked and seems to flake-off already during PEO processing, thus at longer treatment times the coating thickness is not increasing anymore. To prevent extensive flaking-off of the coating a constant voltage PEO “repair” mode was introduced partly successfully at the end of the treatment. %0 journal article %@ 1996-1944 %A Mir, Z.M.,Bastos, A.,Höche, D.,Zheludkevich, M.L. %D 2020 %J Materials %N 6 %P 1426 %R doi:10.3390/ma13061426 %T Recent Advances on the Application of Layered Double Hydroxides in Concrete—A Review %U https://doi.org/10.3390/ma13061426 6 %X The issue of chloride induced corrosion of reinforced concrete is a serious problem affecting infrastructure globally and causing huge economic losses. As such this issue has gained a considerable attention in the scientific community in the recent past. Layered Double Hydroxides (LDHs) have recently emerged as a new class of concrete-additives with a potential to increase the chloride resistance of concrete and mitigate corrosion. LDHs are clay like structures consisting of positively charged layers of cations with associated hydroxides and exchangeable anions in between the layers. Due to this charge balanced structure, LDHs possess the property of encapsulating an anion from the environment and replacing it with an exchangeable anion present in its layers. Potential applications include chloride entrapment in concrete and delivery of corrosion inhibiting anions. However, many versatile compositions of LDHs can be easily synthesized and their application as cement additives reach far beyond corrosion mitigation in concrete. This review presents a summary of recent advances on the applications of LDH in concrete. An extensive set of recently published literature has been critically reviewed and trends have been identified. %0 journal article %@ 0965-0393 %A Mir, Z.M.,Friis, J.,Hagelien, T.F.,Svenum, I.-H.,Ringdalen, I.G.,Konchakova, N.,Zheludkevich, M.L.,Höche, D. %D 2020 %J Modelling and Simulation in Materials Science Engineering %N 2 %P 025003 %R doi:10.1088/1361-651X/ab6209 %T Interoperability architecture for bridging computational tools: application to steel corrosion in concrete %U https://doi.org/10.1088/1361-651X/ab6209 2 %X A multiscale modelling framework, especially for corrosion modelling, requires not only robust computational tools but also an efficient datacentric architecture for handling information exchange at different modelling scales. Different computational solvers require and produce data in different programming languages and specific formats signifying a strong non-uniformity for an easy nexus with other solvers. This non-uniformity has created a need to focus on intermittent state-of-the-art datacentric software tools which aim to bridge data exchange heterogeneity across diverse set of solvers. Data organization in the form of metadata structures are presented as a standard for a coherent information representation regardless of the diverse nature of data formats specific to a scientific discipline. This fundamental work presents the concept, underlying terminology and working mechanism of a datacentric architecture tool SOFT5 for exchanging and interfacing data-flow between solvers and its present application to a concrete technology multiscale simulation network as a potential application. %0 journal article %@ 2296-8016 %A Silva Campos, M.R.,Blawert, C.,Mendis, C.L.,Mohedano, M.,Zimmermann, T.,Proefrock, D.,Zheludkevich, M.L.,Kainer, K.U. %D 2020 %J Frontiers in Materials %N %P 84 %R doi:10.3389/fmats.2020.00084 %T Effect of Heat Treatment on the Corrosion Behavior of Mg-10Gd Alloy in 0.5% NaCl Solution %U https://doi.org/10.3389/fmats.2020.00084 %X In 0.5 wt.% NaCl aqueous solution, Mg-10Gd alloy shows promising corrosion resistance. The microstructure of this alloy was modified via heat treatments to understand the effect of accompanying microstructural changes on the corrosion resistance. It was found that corrosion performance depends both on the amount and the distribution of the cathodic intermetallic phases. The T4 heat treatment (24 h at 540°C) caused the Gd to distribute uniformly in the matrix, which had positive effect on corrosion resistance showing a delay in the time required for the first observation of localized corrosion. The T4 heat treated specimens, specimens aged at 200°C and 300°C, showed relatively uniform degradation and thus these heat treatments are not detrimental in terms of corrosion resistance. In contrast, heat treatment at 400°C seems to increase the formation of small cuboidal particles rich in Gd, most likely to be GdH2 particles, in the matrix, resulting in a detrimental effect on the corrosion behavior. %0 journal article %@ 2213-9567 %A Rakoch, A.,Monakhova, E.,Khabibullina, Z.,Serdechnova, M.,Blawert, C.,Zheludkevich, M.,Gladkova, A. %D 2020 %J Journal of Magnesium and Alloys %N 3 %P 587-600 %R doi:10.1016/j.jma.2020.06.002 %T Plasma-electrolytic oxidation of AZ31 and AZ91 magnesium alloys: comparison of coatings formation mechanism %U https://doi.org/10.1016/j.jma.2020.06.002 3 %X The growth kinetics of PEO coatings on AZ31 and AZ91 magnesium alloys were studied and correlated with their structure, compositions (phase and elemental) and corrosion resistance. It was established that the coatings have a two- (outer and anodic) or three-layer structure (outer, inner and anodic) depending on the treatment time. Briefly, at short treatment time only an anodic layer and outer layer exists. Growth of the outer PEO layer takes place due to the micro discharges, which occur in vertical pores and voids with spherical cross-section. If the time is increasing, and electrolyte inside of the pores is heating-up, etching of the Mg substrate and oxide film becomes more dominant and horizontal pores in the interface between coating and metal are formed. In the pores new anodic layer will form and at this time the formation of the third inner layer starts. The growth of the inner layer happens via the anodic film as a result of micro discharge ignition in the horizontal pores, accompanied by formation of plasma in numerous micro-voids of this layer. The coatings formed on AZ91 alloy are denser, than those on AZ3, which is related to the difference in the rates of inner layer growth and dissolving of oxides which are located at the bottom of the horizontal pores. Because of the lower Al content, the AZ31 substrate itself and the also the oxide films are less stable and tend to dissolve at a higher rate compared to AZ91.,Thus, it was demonstrated that a good corrosion resistance of the coatings was only obtained on AZ91 and if the average thickness of the coating is around 50 µm, correlating with the formation of a sufficiently dense inner layer. Knowing this mechanism, a new two-step treatment was suggested, combining the standard PEO treatment with a subsequent PEO process in an electrolyte supporting the inner film formation. The concept was successfully applied and a further improved corrosion resistance was obtained compared to the single stage PEO process. This improvement of corrosion resistance was related to the better sealing of porosity and formation of a denser inner layer. %0 journal article %@ 0010-938X %A Jiang, P.,Blawert, C.,Scharnagl, N.,Bohlen, J.,Zheludkevich, M. %D 2020 %J Corrosion Science %N %P 108863 %R doi:10.1016/j.corsci.2020.108863 %T Mechanistic understanding of the corrosion behavior of Mg4Zn0.2Sn alloys: from the perspective view of microstructure %U https://doi.org/10.1016/j.corsci.2020.108863 %X The corrosion behavior of as-cast and extruded Mg4Zn0.2Sn (wt.%) alloys was comprehensively compared in 0.5 wt.% NaCl solution. Microstructure and surface chemistry related corrosion performance has been revealed. Zinc-supersaturated solid solution is formed around the intermetallics in the as-cast alloy, but zinc alternately segregates between the α-Mg matrix in the extruded alloy. According to Scanning Kelvin Probe Force Microscopy and immersion tests, micro-galvanic corrosion between the precipitates (intermetallics or impurity particles) or Zinc-rich area and the matrix resulted in severe localized corrosion in both conditions. However, alternation of microstructure induced by extrusion significantly enhanced the corrosion resistance of Mg4Zn0.2Sn alloy. %0 journal article %@ 0169-4332 %A Bouali, A.C.,Iuzviuk, M.H.,Serdechnova, M.,Yasakau, K.A.,Wieland, D.C.F.,Dovzhenko, G.,Maltanava, H.,Zobkalo, I.A.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2020 %J Applied Surface Science %N %P 144027 %R doi:10.1016/j.apsusc.2019.144027 %T Zn-Al LDH growth on AA2024 and zinc and their intercalation with chloride: Comparison of crystal structure and kinetics %U https://doi.org/10.1016/j.apsusc.2019.144027 %X The dissimilarities and features of the crystal structure of ZnAl LDH-NO3 conversion layers grown directly on pure zinc and aluminum alloy 2024 were investigated in the present paper. Although the nature of the cations in the double hydroxides are the same in both cases (Al3+ and Zn2+), their sources differ according to the substrate. This leads to a difference in the cationic layers and interlayer structure, which consequently influences the anionic exchange reaction. In the frame of this work, the kinetics of the anion-exchange of nitrate by chloride was investigated as well as the crystal structure of the resulting ZnAl LDH-Cl on both substrates. Synchrotron high-resolution X-ray diffraction was the main method to obtain structural information and was supported by additional calculations and scanning electron microscopy.,The current study revealed noticeable changes on the positioning of the interlayer atoms for the ZnAl-LDH-Cl on zinc in comparison with the ones on AA2024 substrate. %0 journal article %@ 0010-938X %A Mei, D.,Lamaka, S.,Lu, X.,Zheludkevich, M. %D 2020 %J Corrosion Science %N %P 108722 %R doi:10.1016/j.corsci.2020.108722 %T Selecting medium for corrosion testing of bioabsorbable magnesium and other metals – A critical review %U https://doi.org/10.1016/j.corsci.2020.108722 %X Corrosion testing of bioabsorbable metallic materials is important at material selection stage and for understanding their degradation mechanisms. A large variety of different corrosive media has been reported for evaluating degradation performance. This review takes magnesium as an example and focuses on discussing the advantages, shortcomings and applicability of commonly used corrosive media. The discrepancies between the published results disclosing Mg corrosion behavior often originate from non-comparable test media. This indicates the urgent need for verified corrosion test protocols. The media selection criteria are outlined. Additionally, the discussion extends to the other bioabsorbable metallic materials, such as zinc and iron. %0 journal article %@ 0013-4686 %A Fockaert, L.,Würger, T.,Unbehau, R.,Boelen, B.,Meißner, R.,Lamaka, S.,Zheludkevich, M.,Terryn, H.,Mol, A. %D 2020 %J Electrochimica Acta %N %P 136166 %R doi:10.1016/j.electacta.2020.136166 %T ATR-FTIR in Kretschmann configuration integrated with electrochemical cell as in situ interfacial sensitive tool to study corrosion inhibitors for magnesium substrates %U https://doi.org/10.1016/j.electacta.2020.136166 %X Integrated attenuated total reflection – Fourier transform infrared spectroscopy (ATR-FTIR) – Electrochemical impedance spectroscopy (EIS) measurements were used to simultaneously follow chemisorption mechanisms of organic inhibitors as well as their corrosion inhibition efficiency towards magnesium based substrates. Four carboxylic compounds, i.e. 2,5-pyridinedicarboxylic acid (PDC), 3-methylsalicylic acid (MSA), sodium salicylate (SS) and fumaric acid (FA), were selected based on their promising inhibiting capacities and were all shown to chemisorb at the MgO/Mg(OH)2 surface by carboxylate bond formation. Orientation analysis using polarized infrared light showed that carboxylate bonds established using aliphatic carboxylate compound aligned perpendicular to the magnesium surface, whereas carboxylate bonds with aromatic compounds were oriented in plane with the magnesium surface. This different orientation is associated to the involvement of π-interactions in the MgO/Mg(OH)2 – aromatic carboxylate adsorption. Additionally, DFT calculations revealed that the addition of hetero-atoms (i.e. N or OH) in the molecular structure contributes to increased adsorption energies, indicating that next to carboxylate groups also these hetero-atoms are involved in interfacial interactions. Integrating the ATR-FTIR setup with an electrochemical cell allowing for simultaneous EIS measurements lead to two surface phenomena determining the inhibition efficiency. Surface hydroxylation processes on one hand forming a MgO/Mg(OH)2 layer on one hand, and the chemisorption of carboxylate compounds on the other hand. The inhibition efficiency was found to increase in following order: FA < PDC < MSA and was mainly associated to the formation of a MgO/Mg(OH)2 layer. SS was shown to act as a corrosion accelerator rather than a corrosion inhibitor. Despite its high sensitivity for water, both surface processes could be followed in situ by means of ATR-FTIR. Simultaneously, protective properties of the formed films could be quantified by means of EIS. Consequently, integrated ATR-FTIR – EIS methodology has shown to be highly valuable for gaining in-situ insights in the inhibition mechanism, while quantifying the inhibition efficiency. This was even possible for highly active metal substrate as magnesium, although further developments are suggested if one aims to quantify electrochemical constants related to corrosion and other surface processes measured at the low frequencies (i.e. < 1 Hz). %0 journal article %@ 1463-9076 %A Iuzviuk, M.,Bouali, A.,Serdechnova, M.,Yasakau, K.,Wieland, F.,Dovzhenko, G.,Mikhailau, A.,Blawert, C.,Zobkalo, I.,Ferreira, M.,Zheludkevich, M. %D 2020 %J Physical Chemistry Chemical Physics %N 31 %P 17574-17586 %R doi:10.1039/D0CP01765E %T In situ kinetics studies of Zn–Al LDH intercalation with corrosion related species %U https://doi.org/10.1039/D0CP01765E 31 %X Kinetic parameters for three anion exchange reactions – Zn-LDH-NO3 → Zn-LDH-Cl, Zn-LDH-NO3 → Zn-LDH-SO4 and Zn-LDH-NO3 → Zn-LDH-VOx – were obtained by in situ synchrotron study. The first and the second ones are two-stage reactions; the first stage is characterized by the two-dimensional diffusion-controlled reaction following deceleratory nucleation and the second stage is a one-dimensional diffusion-controlled reaction also with a decelerator nucleation effect. In the case of exchange NO3− → Cl− host anions are completely released, while in the case of NO3− → SO42− the reaction ends without complete release of nitrate anions. The exchange of Zn-LDH-NO3 → Zn-LDH-VOx is a one-stage reaction and goes much slower than the previous two cases. The latter is characterized by a one stage two-dimensional reaction with an instantaneous nucleation. As a result, at the end of this process there are two crystalline phases with different polyvanadate species, presumably V4O124− and V2O74−, nitrate anions were not completely released. The rate of replacing NO3− anions by guest ones can be represented as Cl− > SO42− > VOxy−. %0 journal article %@ 1463-9076 %A Zec, N.,Mangiapia, G.,Zheludkevich, M.,Busch, S.,Moulin, J. %D 2020 %J Physical Chemistry Chemical Physics %N 21 %P 12104-12112 %R doi:10.1039/c9cp06779e %T Revealing the interfacial nanostructure of a deep eutectic solvent at a solid electrode %U https://doi.org/10.1039/c9cp06779e 21 %X Deep eutectic solvents (DESs) are both green and sustainable, making them an increasingly attractive alternative to conventional solvents. One of their applications is the electrochemical deposition of metals that cannot be deposited from aqueous solution because of the limited electrochemical window of water. The electrodeposition process is influenced by the structure and dynamics of the solvent at the solid–liquid interface. Therefore,the nanoscale structure of the interface between a silicon substrate and deep eutectic solvent (choline chloride–ethylene glycol) was studied by neutron reflectometry (NR) and molecular dynamics (MD) simulations. It is not possible to model NR measurements of this system without simulating a dense DES layer at the solid–liquid interface. This study used an MD simulation trajectory to extract the density, thickness, and roughness of this DES layer. With this input, the model reproduces the reflectometry data at all measured H/D contrasts very well. The thickness of the layer does not change appreciably when applying charge or at higher temperatures. Further analysis revealed a reorganization of ions and reorientation of the choline cations in the interface layer when the electrodes are charged. These changes in ion orientation are not observed with the NR technique since they do not influence the neutron scattering length density profile due to the high number of ethylene glycol molecules at the interface. However, the agreement between measured neutron reflectometry data and model parameters obtained from MD simulations justified subnanoscale analysis of the MD trajectory and confirmed that these two complementary techniques can be successfully combined to reveal the solid/DES interface structure. %0 journal article %@ 1438-1656 %A Mir, Z.,Bastos, A.,Gomes, C.,Mueller, U.,Alonso, M.,Villar, K.,Rabade, M.,Maia, F.,Rocha, C.,Maincon, P.,Höche, D.,Ferreira, M.,Zheludkevich, M. %D 2020 %J Advanced Engineering Materials %N 11 %P 2000398 %R doi:10.1002/adem.202000398 %T Numerical and Experimental Analysis of Self‐Protection in Reinforced Concrete due to Application of Mg–Al–NO2 Layered Double Hydroxides %U https://doi.org/10.1002/adem.202000398 11 %X Concrete possesses an intrinsic chloride binding capacity. Chloride ions from the environment bind with the hydrated cementitious phases in the form of bound chlorides. The contribution of chemically bound chlorides toward increasing the service life of concrete structures is vital as they help in slowing down the chloride diffusion in the concrete thereby delaying reinforcement depassivation. The authors attempt to increase the chloride binding capacity of concrete by adding a small amount of Mg–Al–NO2 layered double hydroxides (LDHs) with the objective to delay reinforcement corrosion and by this to considerably extend the service life of concrete structures situated in harsh environments. This study presents numerical and experimental analysis of the action of LDH in concrete. Formation factor is used to determine the effective chloride diffusion coefficient. In addition, the chloride binding isotherms together with Poisson–Nernst–Planck equations are used to model the chloride ingress. A comparable chloride binding is observed for concrete with and without Mg–Al–NO2, depicting only a slight chloride uptake by Mg–Al–NO2. Further investigations are conducted to understand this behavior by studying the stability and chloride entrapping capacity Mg–Al–NO2 in concrete. %0 journal article %@ 2624-5558 %A Jiang, P.,Blawert, C.,Zheludkevich, M. %D 2020 %J Corrosion and Materials Degradation %N 1 %P 92-158 %R doi:10.3390/cmd1010007 %T The Corrosion Performance and Mechanical Properties of Mg-Zn Based Alloys - A Review %U https://doi.org/10.3390/cmd1010007 1 %X Magnesium alloys have shown great potential for applications as both structural and biomedical materials due to their high strength-to-weight ratio and good biodegradability and biocompatibility, respectively. Among them, Mg-Zn based alloys are attracting increasing interest for both applications. As such, this article provides a review of the corrosion performance and mechanical properties of Mg-Zn based alloys, including the influence of environment and processing on both of them. The strategies for tailoring corrosion resistance and/or mechanical properties by microstructure adjustment and surface treatment are discussed. %0 journal article %@ 1996-1944 %A Gluchowski, P.,Nikonkov, R.,Tomala, R.,Strek, W.,Shulha, T.,Serdechnova, M.,Zheludkevich, M.,Pakalaniskis, A.,Skaudzius, R.,Kareiva, A.,Abramov, A.,Kholkin, A.,Bushinsky, M.V.,Karpinsky, D. %D 2020 %J Materials %N 7 %P 1788 %R doi:10.3390/ma13071788 %T Magnetic Properties of La0.9A0.1MnO3 (A: Li, Na, K) Nanopowders and Nanoceramics %U https://doi.org/10.3390/ma13071788 7 %X Nanocrystalline La0.9A0.1MnO3 (where A is Li, Na, K) powders were synthesized by a combustion method. The powders used to prepare nanoceramics were fabricated via a high-temperature sintering method. The structure and morphology of all compounds were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It was found that the size of the crystallites depended on the type of alkali ions used. The high-pressure sintering method kept the nanosized character of the grains in the ceramics, which had a significant impact on their physical properties. Magnetization studies were performed for both powder and ceramic samples in order to check the impact of the alkali ion dopants as well as the sintering pressure on the magnetization of the compounds. It was found that, by using different dopants, it was possible to strongly change the magnetic characteristics of the manganites. %0 journal article %@ 0378-7753 %A Vaghefinazari, B.,Höche, D.,Lamaka, S.,Snihirova, D.,Zheludkevich, M.L. %D 2020 %J Journal of Power Sources %N %P 227880 %R doi:10.1016/j.jpowsour.2020.227880 %T Tailoring the Mg-air primary battery performance using strong complexing agents as electrolyte additives %U https://doi.org/10.1016/j.jpowsour.2020.227880 %X Mg-air primary battery has become an attractive source of energy due to its economic viability, environmental benignity, and high theoretical specific power density. However, low practical delivered power due to high self-corrosion and fast anode fouling are the main reasons that limit their commercial application. Modification of the electrolyte chemistry in Mg-air batteries plays a crucial role in improving the Mg-air battery performance. In this study, the impact of addition of two strong complexing agents at different concentrations in the aqueous electrolyte of Mg-air battery is investigated. Galvanostatic polarization test is conducted in order to evaluate the discharge performance of the half-cell on the anode side in the presence or absence of strong complexing agents. According to the results, strong complexing agents are able to effectively activate magnesium anode and provide a higher delivered potential. A decrease in the additive concentrations in the electrolyte leads to the attainment of higher utilization efficiency at the expense of slight drop in discharge potential. %0 journal article %@ 1976-0485 %A Mir, Z.M.,Hoeche, D.,Gomes, C.,Sampaio, R.,Bastos, A.C.,Maincon, P.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2019 %J International Journal of Concrete Structures and Materials %N 1 %P 11 %R doi:10.1186/s40069-018-0321-0 %T Enhanced Predictive Modelling of Steel Corrosion in Concrete in Submerged Zone Based on a Dynamic Activation Approach %U https://doi.org/10.1186/s40069-018-0321-0 1 %X A numerical model for enhanced service life prediction of concrete infrastructure is presented which includes transient analysis of processes during corrosion initiation as well as propagation stage. The temporal and spatial transition of Steel–Concrete Interface during depassivation events is described by a randomly varying chloride threshold function. As such random activation events can be accounted for, rather than having to pre-describe the anode size and location as in many existing models. The aim of the study is to investigate random spatial activation events in concrete structures in submerged zones based on dynamically changing boundary conditions on the rebar surface to control transition from passive to active state. Investigations are carried out to realize the sustainability of corrosion processes in limiting oxygen concentrations in dissolved seawater. The model showcases the numerical architecture, the associated concept of randomly varying chloride threshold and predicts that among other factors, the rate of oxygen strongly influences corrosion rate in submerged locations. %0 journal article %@ 0370-1972 %A Kalanda, N.,Haramus, V.M.,Avdeev, M.,Zheludkevich, M.L.,Yarmolich, M.,Serdechnova, M.,Wieland, D.C.F.,Petrov, A.,Zhaludkevich, A.,Sobolev, N. %D 2019 %J Physica Status Solidi B %N 5 %P 1800428 %R doi:10.1002/pssb.201800428 %T Small‐Angle Neutron Scattering and Magnetically Heterogeneous State in Sr2FeMoO6–δ %U https://doi.org/10.1002/pssb.201800428 5 %X Single‐phase strontium ferromolybdate (Sr2FeMoO6–δ) samples with different degrees of the superstructural ordering of the Fe/Mo cations (P) are obtained from partially reduced SrFeO3–х, SrMoO4 precursors by the solid‐state technology. The study of the temperature dependences of the magnetization measured in the field‐cooling and zero‐field‐cooling modes indicated an inhomogeneous magnetic state of the samples. The presence of magnetic regions of different nature has also been revealed by the small‐angle neutron scattering. For the Sr2FeMoO6–δ samples with different P values and for all values of the magnetic field induction up to 1.5 T and of the scattering vector in the interval 0.1 > q > 0.002 Å−1, the analytical dependence I ∼ q–α obeys the Porod law (α ≈ 4), which corresponds to an object with a smooth and well‐marked surface and polydisperse grain size. Deviations from the Porod law in the q > 0.1 Å−1 region and a weakening of the neutron scattering in applied magnetic fields may be ascribed to magnetic inhomogeneities with diameters D < 6 nm, which are partially destroyed/oriented by magnetic fields В ≥ 1.5 T. It is established that the magnetic homogeneity of the Sr2FeMoO6–δ compound is enhanced with increasing superstructural ordering of the Fe/Mo cations. %0 journal article %@ 0013-4686 %A Martins Queiroz, F.,Donatus, U.,Prada Ramirez, O.M.,de Sousa Araujo, J.V.,Goncalves de Viveiros, B.V.,Lamaka, S.,Zheludkevich, M.,Masoumi, M.,Vivier, V.,Costa, I.,Gomes de Melo, H. %D 2019 %J Electrochimica Acta %N %P 271-281 %R doi:10.1016/j.electacta.2019.04.137 %T Effect of unequal levels of deformation and fragmentation on the electrochemical response of friction stir welded AA2024-T3 alloy %U https://doi.org/10.1016/j.electacta.2019.04.137 %X The effect of unequal levels of deformation and fragmentation on the electrochemical response of friction stir welded AA2024-T3 has been investigated using electron backscatter diffraction, scanning electron microscopy, global and localized electrochemical techniques. The friction stir welding process introduced unequal distribution and fragmentation of coarse intermetallic particles, such that more clusters of these particles were present in the thermomechanically affected zone of the weld. This resulted in a higher susceptibility to severe localized corrosion in this region when compared with the others. Results from electrochemical measurements using a microcell could not be clearly correlated with the corrosion behaviour because no significant differences were observed using these techniques. On the other hand, LEIS and SVET results were in agreement and correlated with the corrosion evolution at the surfaces of the tested samples. %0 journal article %@ 1996-1944 %A Ofoegbu, S.U.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2019 %J Materials %N 4 %P 651 %R doi:10.3390/ma12040651 %T Galvanically Stimulated Degradation of Carbon-Fiber Reinforced Polymer Composites: A Critical Review %U https://doi.org/10.3390/ma12040651 4 %X Carbon is used as a reinforcing phase in carbon-fiber reinforced polymer composites employed in aeronautical and other technological applications. Under polarization in aqueous media, which can occur on galvanic coupling of carbon-fiber reinforced polymers (CFRP) with metals in multi-material structures, degradation of the composite occurs. These degradative processes are intimately linked with the electrically conductive nature and surface chemistry of carbon. This review highlights the potential corrosion challenges in multi-material combinations containing carbon-fiber reinforced polymers, the surface chemistry of carbon, its plausible effects on the electrochemical activity of carbon, and consequently the degradation processes on carbon-fiber reinforced polymers. The implications of the emerging use of conductive nano-fillers (carbon nanotubes and carbon nanofibers) in the modification of CFRPs on galvanically stimulated degradation of CFRP is accentuated. The problem of galvanic coupling of CFRP with selected metals is set into perspective, and insights on potential methods for mitigation and monitoring the degradative processes in these composites are highlighted. %0 journal article %@ 2296-8016 %A Würger, T.,Feiler, C.,Musil, F.,Feldbauer, G.B.,Höche, D.,Lamaka, S.,Zheludkevich, M.L.,Meißner, R.H. %D 2019 %J Frontiers in Materials %N %P 53 %R doi:10.3389/fmats.2019.00053 %T Data Science Based Mg Corrosion Engineering %U https://doi.org/10.3389/fmats.2019.00053 %X Magnesium exhibits a high potential for a variety of applications in areas such as transport, energy and medicine. However, untreated magnesium alloys are prone to corrosion, restricting their practical application. Therefore, it is necessary to develop new approaches that can prevent or control corrosion and degradation processes in order to adapt to the specific needs of the application. One potential solution is using corrosion inhibitors which are capable of drastically reducing the degradation rate as a result of interactions with the metal surface or components of the corrosive medium. As the sheer number of potential dissolution modulators makes it impossible to obtain a detailed atomistic understanding of the inhibition mechanisms for each additive, other measures for inhibition prediction are required. For this purpose, a concept is presented that combines corrosion experiments, machine learning, data mining, density functional theory calculations and molecular dynamics to estimate corrosion inhibition properties of still untested molecules. Concomitantly, this approach will provide a deeper understanding of the fundamental mechanisms behind the prevention of corrosion events in magnesium-based materials and enables more accurate continuum corrosion simulations. The presented concept facilitates the search for molecules with a positive or negative effect on the inhibition efficiency and could thus significantly contribute to the better control of magnesium / electrolyte interface properties. %0 journal article %@ 0257-8972 %A Atapour, M.,Blawert, C.,Zheludkevich, M.L. %D 2019 %J Surface and Coatings Technology %N %P 626-637 %R doi:10.1016/j.surfcoat.2018.10.033 %T The wear characteristics of CeO2 containing nanocomposite coating made by aluminate-based PEO on AM 50 magnesium alloy %U https://doi.org/10.1016/j.surfcoat.2018.10.033 %X This study examined the influence of CeO2 nanoparticles on the wear characteristics of aluminate-based PEO coatings formed on the AM50 magnesium alloy, which was developed for the automotive industry. Sliding wear assessments were conducted on a ball-on-disk tribometer at 2 N, 5 N and 10 N loads (against an AISI 52100 steel ball). It was found that the wear characteristics were greatly affected by the addition of CeO2 nanoparticles, especially under intermediate and high loads. The coatings with and without CeO2 remained intact during the sliding test at 2 N. Under an intermediate load of 5 N, the coating treated in the absence of CeO2 failed, while the one made in the presence of CeO2 offered superior wear resistance without any signs of wear failure. Under the 10 N load, the CeO2-free coating was completely removed and the substrate emerged, which was mainly due to a combined adhesive–abrasive wear damage mechanism; in contrast, the CeO2-containing coating (PEO-CeO2) offered much superior wear resistance to the Mg alloy, which was consistent with the friction coefficient data. SEM-EDS analysis of the worn surface of the steel balls also indicated that the transfer of the coating fragments to the ball surface was more intensive for the nanoparticle-free coating, as compared to that observed for the PEO-CeO2 coating. Also, the appearance of some deep scoring in the worn surface of the balls could be considered as a result of the three-body abrasive wear. The superior wear resistance of the CeO2 embedded nanocomposite coating could be mainly attributed to its lower porosity, lower roughness, and higher hardness. %0 journal article %@ 0925-8388 %A Jiang, P.,Blawert, C.,Hou, R.,Scharnagl, N.,Bohlen, J.,Zheludkevich, M.L. %D 2019 %J Journal of Alloys and Compounds %N %P 179-192 %R doi:10.1016/j.jallcom.2018.12.296 %T Microstructural influence on corrosion behavior of MgZnGe alloy in NaCl solution %U https://doi.org/10.1016/j.jallcom.2018.12.296 %X The corrosion behavior of a novel Mg0.5Zn0.2Ge alloy in as-cast and extruded conditions is investigated in 0.9 wt.% NaCl solution. Scanning kelvin probe force microscopy measurements and local electrolyte drop corrosion tests demonstrated that the matrix dissolved preferentially in corrosive solution due to the nobler Volta potential of the Mg2Ge phase. A combination of potentiodynamic polarization, electrochemical impedance spectroscopy, hydrogen evolution and weight loss tests illustrated and quantified the corrosion performance of Mg0.5Zn (Control) and Mg0.5Zn0.2Ge alloys. The results revealed that the corrosion resistance of the Mg0.5Zn alloy was improved by micro-alloying with germanium (Ge) due to decreased cathodic kinetics. Furthermore, the corrosion resistance of the Mg0.5Zn0.2Ge alloy was enhanced by hot extrusion. According to element mapping analysis of the cross section of the alloys after corrosion, the improved corrosion resistance of extruded Mg0.5Zn0.2Ge alloy could be attributed to the increased incorporation of Zn and Ge elements in the outer layer of the corrosion products film. %0 journal article %@ 0010-938X %A Mei, D.,Lamaka, S.V.,Gonzalez, J.,Feyerabend, F.,Willumeit-Roemer, R.,Zheludkevich, M.L. %D 2019 %J Corrosion Science %N %P 81-93 %R doi:10.1016/j.corsci.2018.11.011 %T The role of individual components of simulated body fluid on the corrosion behavior of commercially pure Mg %U https://doi.org/10.1016/j.corsci.2018.11.011 %X Simulated body fluid (SBF) is a common medium for in vitro corrosion analysis. The individual influence and synergy of the SBF components on the corrosion of commercially pure Mg are investigated in this study. The results demonstrate that corrosion acceleration in presence of the synthetic pH buffer, Tris/HCl, is attributed to the combined effect of three factors: increased Cl− concentration, complexation of Mg2+ and Ca2+ and consumption of OH− needed for products formation. In Tris/HCl-free SBF, the synergy between Ca2+, Mg2+, HPO42- and HCO3− assures slowest Mg degradation due to growth of partially protective layer that becomes thicker with time. %0 journal article %@ 0010-938X %A Snihirova, D.,Hoeche, D.,Lamaka, S.,Mir, Z.,Hack, T.,Zheludkevich, M.L. %D 2019 %J Corrosion Science %N %P 70-78 %R doi:10.1016/j.corsci.2019.04.036 %T Galvanic corrosion of Ti6Al4V -AA2024 joints in aircraft environment: Modelling and experimental validation %U https://doi.org/10.1016/j.corsci.2019.04.036 %X This study focuses on the development of a physico-chemical model based on mechanistic and kinetics understanding of the corrosion process in galvanic couple Ti6Al4V-AA2024. Proposed model provides deeper insights at macro level for initiation and propagation of localized corrosion of AA2024 in galvanically coupled multi-material assemblies. The model is able to reveal the localized corrosion, related to heterogeneity of AA2024 microstructure, including local pH changes, the deposition of the reaction products, and emphasizes the important role of AA2024 self-corrosion in galvanic assemblies. The validation of the developed model was performed using relevant data collected by advanced in situ localized techniques. %0 journal article %@ 2590-1508 %A Entringer, J.,Meisnar, M.,Reimann, M.,Blawert, C.,Zheludkevich, M.,dos Santos, J.F. %D 2019 %J Materials Letters: X %N %P 100014 %R doi:10.1016/j.mlblux.2019.100014 %T The effect of grain boundary precipitates on stress corrosion cracking in a bobbin tool friction stir welded Al-Cu-Li alloy %U https://doi.org/10.1016/j.mlblux.2019.100014 %X Evidence of stress corrosion cracking has been observed in exposed semi-stationary bobbin tool friction stir welded aluminum-copper-lithium alloy 2060-T8. Microstructural analysis confirmed the heterogeneous microstructure transformation caused by the thermomechanical impact of the welding process. Grain boundary phase accumulation initiated anodic dissolution in NaCl solution under stress. In the center and the heat affected zone of the weld, the microstructure was found to form overaged and high copper containing equilibrium phases promoting intergranular stress corrosion. %0 journal article %@ 0925-8388 %A Liu, W.,Blawert, C.,Zheludkevich, M.L.,Lin, Y.,Talha, M.,Shi, Y.,Chen, L. %D 2019 %J Journal of Alloys and Compounds %N %P 996-1007 %R doi:10.1016/j.jallcom.2019.03.060 %T Effects of graphene nanosheets on the ceramic coatings formed on Ti6Al4V alloy drill pipe by plasma electrolytic oxidation %U https://doi.org/10.1016/j.jallcom.2019.03.060 %X Ceramic coatings were formed on the surface of Ti6Al4V alloy drill pipe by plasma electrolytic oxidation (PEO) technology in the silicate electrolyte with and without graphene nanosheets. Voltage-time responses were recorded. The microstructure, elements distribution and phase composition were investigated by SEM, TEM, EDS and XRD. The basic physical properties and wear resistance were studied. The morphology of wear tracks was observed by SEM and three-dimensional microscope. Results indicated graphene nanosheets successfully incorporated in the ceramic coating. The main elemental components were Ti, Si and O. They were crystallized and composed of anatase and rutile. The coating with graphene nanosheets showing the morphology and structure of flatter and less pores was superior to the coating without graphene nanosheets exhibiting rugged and more pores, and the microhardness of the coating with graphene nanosheets was 1250 HV which was noteworthy improved in contrast with the coating without graphene nanosheets of 870 HV. Wear test results showed the coating with graphene nanosheets displayed extremely significant wear resistance due to the physical barrier of graphene nanosheets. In summary, the application of graphene nanosheets to improve the wear resistance of titanium alloy drill pipe is a promising and promotional research. %0 journal article %@ 0010-938X %A Mei, D.,Lamaka, S.V.,Feiler, C.,Zheludkevich, M.L. %D 2019 %J Corrosion Science %N %P 258-271 %R doi:10.1016/j.corsci.2019.03.039 %T The effect of small-molecule bio-relevant organic components at low concentration on the corrosion of commercially pure Mg and Mg-0.8Ca alloy: An overall perspective %U https://doi.org/10.1016/j.corsci.2019.03.039 %X The individual and combined influence of 53 small molecule bio-relevant organic compounds on the corrosion of CP Mg and Mg-0.8Ca is investigated. The results demonstrate that tested amino acids, vitamins and saccharides, do not critically influence the in vitro corrosion of tested materials. The presence of penicillin and streptomycin at low concentration in MEM has no significant influence on the corrosion, while higher concentration of streptomycin accelerates degradation. The similarity between MEM and SBF as corrosive medium for in vitro tests is also clarified. These results contribute to understanding the influence of organic compounds on in vitro corrosion of Mg. %0 journal article %@ 2213-3437 %A Smazna, D.,Shree, S.,Polonskyi, O.,Lamaka, S.,Baum, M.,Zheludkevich, M.,Faupel, F.,Adelung, R.,Kumar Mishra, Y. %D 2019 %J Journal of Environmental Chemical Engineering %N 2 %P 103016 %R doi:10.1016/j.jece.2019.103016 %T Mutual interplay of ZnO micro- and nanowires and methylene blue during cyclic photocatalysis process %U https://doi.org/10.1016/j.jece.2019.103016 2 %X Water purification through photocatalysis is the most important requirement due to the increased health, environmental and energy conservation concerns. Metal oxide nanostructures have played a very prominent role in this direction. ZnO is a promising material in terms of nanostructuring and photocatalysis. This study presents a unique easy-to-follow synthesis for ZnO micro- and nanowires by a flame-based approach. The photocatalytic activity of these grown ZnO nano- and microwires against methylene blue (MB) has been investigated in detail and a possible decomposition pathway is proposed. During repeated photocatalysis, a significant improvement in the decomposition rate was achieved which is mainly attributed to surface modifications of the ZnO wires due to the reaction with MB as confirmed by Raman-spectroscopy and X-ray photoelectron spectroscopy (XPS) investigations. The impact of the MB over involved nanostructures is thus an important aspect for the efficiency of the photocatalysis which is briefly presented here. %0 journal article %@ 1002-0071 %A Han, J.,Blawert, C.,Yang, J.,Lu, X.,Hu, J.,Zheludkevich, M. %D 2019 %J Progress in Natural Science: Materials International %N 1 %P 94-102 %R doi:10.1016/j.pnsc.2019.01.010 %T Self-cleaning property of AZ31 Mg alloy during plasma electrolytic oxidation process %U https://doi.org/10.1016/j.pnsc.2019.01.010 1 %X The rolling of metal sheet often leads to strong contamination of the resulting surface. The present work reports the effects of the surface contamination remaining after rolling of AZ31 Mg alloy on plasma electrolytic oxidation (PEO) treatment of the resulting sheet material. Results indicate that most of the contaminants on the surface of as-rolled AZ31 Mg alloy are removed in the early stages of PEO process. The contaminations slightly influence the phase composition of PEO coating. Non-uniform distribution of contaminations results in aggregation of pores on the surface of PEO samples. On the bare substrate the contaminations are responsible for poor wear and corrosion resistance but final PEO coatings reveals similar performance on contaminated substrate compared to the abraded one. A self-cleaning property of the PEO and possibility of one step process, avoiding pre-cleaning stages, is suggested. %0 journal article %@ 0169-4332 %A Bouali, A.C.,Straumal, E.A.,Serdechnova, M.,Wieland, D.C.F.,Starykevich, M.,Blawert, C.,Hammel, J.U.,Lermontov, S.A.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2019 %J Applied Surface Science %N %P 829-840 %R doi:10.1016/j.apsusc.2019.07.117 %T Layered double hydroxide based active corrosion protective sealing of plasma electrolytic oxidation/sol-gel composite coating on AA2024 %U https://doi.org/10.1016/j.apsusc.2019.07.117 %X This work reports a novel approach for growing layered double hydroxide (LDH) films on any plasma electrolytic oxidation (PEO) coated AA2024 independently of the nature of the PEO coating. The specific PEO coating chosen to carry out this work is considered to be not suitable for direct LDH growth because of phase composition and morphological features. In this paper, we describe a new methodology that consists of covering the PEO coating with a thin layer of aluminum oxide based xerogel as the source of aluminate ions for subsequent in-situ LDH growth. X-ray diffraction (XRD) and scanning electron microscope (SEM) images showed a successful formation of LDHs on the surface. An improvement in terms of active corrosion protection was also demonstrated by electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). %0 journal article %@ 2079-6412 %A Neves, C.,Bastos, A.,Salak, A.,Starykevich, M.,Rocha, D.,Cunha, A.,Almeida, A.,Zheludkevich, M.,Tedim, J.,Ferreira, M. %D 2019 %J Coatings %N 5 %P 328 %R doi:10.3390/coatings9050328 %T Layered Double Hydroxide Clusters as Precursors of Novel Multifunctional Layers: A Bottom-Up Approach %U https://doi.org/10.3390/coatings9050328 5 %X The specific microstructure of aluminum alloys is herein explored to grow spatially-resolved layered double hydroxide (SR-LDH) clusters on their surface. Upon chemical modification of LDHs via intercalation, adsorption and grafting with different functional molecules, novel surface-engineered surfaces were obtained. Crystal structure and phase composition were analyzed by X-ray diffraction (XRD) and surface morphology was observed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectrometry (GDOES) were used to correlate structural changes upon ion-exchange and interfacial modifications with chemical composition and surface profiles of the SR-LDH films, respectively. The protection conferred by these films against localized corrosion was investigated at microscale using the scanning vibrating electrode technique (SVET). LDH-NO3 phase was obtained by direct growth onto AA2024 surface, as evidenced by (003) and (006) XRD diffraction reflections. After anion exchange of nitrate with 2-mercaptobenzothiazole (MBT) there was a decrease in the SR-LDH thickness inferred from GDOES profiles. The subsequent surface functionalization with HTMS was confirmed by the presence of Si signal in XPS and GDOES analyses, leading to an increase in the water contact angle (c.a 144° ± 3°). SVET measurements of the SR-LDH films revealed exceptional corrosion resistance, whereas the bioluminescent bacteria assay proved the anti-microbial character of the obtained films. Overall the results obtained show an effective corrosion protection of the SR-LDHs when compared to the bare substrate and the potential of these films for biofouling applications as new Cr-free pre-treatments. %0 journal article %@ 0378-7753 %A Deng, M.,Wang, L.,Höche, D.,Lamaka, S.,Snihirova, D.,Vaghefinazari, B.,Zheludkevich, M. %D 2019 %J Journal of Power Sources %N %P 227201 %R doi:10.1016/j.jpowsour.2019.227201 %T Clarifying the decisive factors for utilization efficiency of Mg anodes for primary aqueous batteries %U https://doi.org/10.1016/j.jpowsour.2019.227201 %X Low anodic efficiency of metallic Mg, which results in low discharge capacity and specific energy density, hinders the wider application of aqueous primary Mg batteries. In this work, we clarify the decisive factors effecting the utilization efficiency of Mg anodes. Anodic efficiency of several Mg anodes at different current densities is measured in 3.5 wt% NaCl electrolyte. The contribution of self-corrosion at open circuit potential and at constant applied current to efficiency of Mg anodes is compared. Additionally, efficiency loss caused by detachment of undissolved metallic portions, namely “chunk effect”, is determined with a proposed new approach. The effect of self-corrosion and “chunk effect” on anodic efficiency is assessed accordingly. The results indicate that “chunk effect” can also result in large efficiency loss of Mg anodes, especially at low current densities, which, in some cases, could exceed the loss caused by other mechanisms of self-corrosion of anode substrate. Hence, attention should be paid to both aspects when developing novel Mg anodes with high anodic efficiency, particularly for application in long-term low-power battery system. %0 journal article %@ 0010-938X %A Deng, M.,Höche, D.,Lamaka, S.,Wang, L.,Zheludkevich, M. %D 2019 %J Corrosion Science %N %P 225-235 %R doi:10.1016/j.corsci.2019.03.050 %T Revealing the impact of second phase morphology on discharge properties of binary Mg-Ca anodes for primary Mg-air batteries %U https://doi.org/10.1016/j.corsci.2019.03.050 %X Mg-0.5 (wt.%)Ca alloys with different microstructures are prepared through casting followed by different cooling rates. The impact of microstructure, especially second phase morphology, on self-corrosion and discharge performance of Mg-0.5Ca alloys is investigated. The water-cooled Mg-0.5Ca alloy shows a lower self-corrosion rate than the air-cooled one and enables the Mg-air cell to possess increased utilization efficiency and enhanced energy density. Intermittent discharge tests are performed to study the battery performance after no-discharge intervals. All results indicate that the water-cooled Mg-0.5Ca cast alloy could be a promising anode material for aqueous Mg-air batteries with long-term storage and under intermittent discharge. %0 journal article %@ 2305-6894 %A Chirkunov, A.,Rakoch, A.,Monakhova, E.,Gladkova, A.,Khabibullina, Z.,Ogorodnikova, V.,Serdechnova, M.,Blawert, C.,Kuznetsov, Y.,Zheludkevich, M. %D 2019 %J International Journal of Corrosion and Scale Inhibition %N 4 %P 1170-1188 %R doi:10.17675/2305-6894-2019-8-4-22 %T Corrosion protection of magnesium alloy by PEO-coatings containing sodium oleate %U https://doi.org/10.17675/2305-6894-2019-8-4-22 4 %X The kinetics of plasma-electrolytic oxidation (PEO) coating growth on AZ31 alloy in an alkaline–phosphate–aluminate electrolyte was studied. The structure, elemental composition and corrosion resistance of obtained PEO coatings were studied as a function of thickness. It was established that formation of the coating layers takes place in the following sequence: anodic, external and internal layers. Their formation occurs due to: 1) dielectric layer formation due to anodic conversion of surface; 2) ignition of powerful microdischarges in the transversal pores of the initially formed coating, forming the main part of its outer layer in case of increasing duration of the PEO process; 3) etching of magnesium alloy as a result of electrolyte penetration through the transversal pores to the metal substrate, followed by its anodizing; 4) ignition of microdischarges under the coatings outer layer, leading to formation of an inner layer. Existence of the coating inner layer causes a significant increase in corrosion resistance; however, it is still insufficient for long-lasting standalone corrosion protection. It was shown that sodium oleate (SOl) is the best inhibitor for the AZ31 substrate, therefore it was selected for impregnating PEO coatings. Impregnation of the coatings in 10 mM SOl solution increases their protective ability. Corrosion tests of PEO coated AZ31 samples in a climate chamber showed that the effect of impregnating is most pronounced for thin PEO coatings (20 μm). Under more corrosive conditions of salt spray test, impregnating the PEO coating with SOl increased the time until the appearance of the first corrosion marks. It also significantly slowed down the development of the corrosion marks compared with the samples coated by PEO without impregnation. %0 journal article %@ 0010-938X %A Andre, N.M.,Bouali, A.,Maawad, E.,Staron, P.,dos Santos, J.F.,Zheludkevich, M.L.,Amancio-Filho, S.T. %D 2019 %J Corrosion Science %N %P 108075 %R doi:10.1016/j.corsci.2019.07.002 %T Corrosion behavior of metal–composite hybrid joints: Influence of precipitation state and bonding zones %U https://doi.org/10.1016/j.corsci.2019.07.002 %X The corrosion behavior of AA2024-T3/carbon-fiber-reinforced polyphenylene sulfide joints was investigated. The joints were exposed to salt spray from one to six weeks. The residual strength of these joints was assessed using lap shear test. The corroded surfaces and interfaces were analyzed using small angle X-ray scattering, scanning electron microscopy, and energy dispersive spectroscopy. Regarding the top surface of the joints, the aluminum part corroded preferably in the heat-affected zone (HAZ). It was demonstrated that the HAZ is more susceptible to corrosion than the stir zone (SZ) due to the anodic sites formed by coarse intermetallic particles and S’(S) phase precipitation. Besides, the macro-galvanic coupling between the zones may also potentialize the corrosion in HAZ as the base material and SZ displayed a lower volume fraction of S’(S) than HAZ. In addition, the corrosion at the interface of the joints was evaluated. Four different stages in the development of corrosion at the interface were identified. At Stage I, the joints showed fast strength degradation (0% to -24% of ultimate lap shear force (ULSF) due to water absorption and NaCl migration into the composite. At Stage II, the strength degradation of the joints was stalled (-24% to -28% of ULSF) due to the protection provided to the bonding area by the reconsolidated layer of polymer at the borders of the joint. The polymeric layer acted as a protective coating on the aluminum surface. At Stage III, the corrosion overcame the polymeric layer by reaching the bonding area of the joint. As a result, the strength of the joints rapidly degraded from -28% to -44% of ULSF. Finally, at Stage IV, one expects generalized corrosion in the bonding area, leading to the final strength degradation of the joint. %0 journal article %@ 0013-4686 %A Snihirova, D.,Lamaka, S.V.,Gonzalez-Garcia, Y.,Yilmaz, A.,Scharnagl, N.,Montemor, M.F.,Zheludkevich, M.L. %D 2019 %J Electrochimica Acta %N %P 134761 %R doi:10.1016/j.electacta.2019.134761 %T Influence of inhibitor adsorption on readings of microelectrode during SVET measurements %U https://doi.org/10.1016/j.electacta.2019.134761 %X One of the main applications of SVET in corrosion research is the study of the corrosion inhibition effectiveness and the evaluation of the self-healing effect of inhibitor-containing coatings. The tip of the platinum/iridium vibrating electrode is electroplated with black platinum, which creates a large electrode surface and confers high capacitance to the tip. When studying organic inhibitors in aqueous solutions with SVET, inhibitor adsorption may occur at the tip, causing its contamination and the initial calibration conditions of the system might not be valid. This may lead to an incorrect interpretation of the results.,This work is intended to study the effect of different inhibitors (cerium nitrate, 8-hydroxyquinoline, potassium 2,5-dimercapto-1,3,4-thiadiazolate, benzotriazole and mercaptobenzothiazole), typically used for corrosion protection of aluminum alloys, on the Pt probe signal during SVET measurements.,The results reveal the detrimental effect of some corrosion inhibitors on the sensitivity of the vibrating probe, an effect that imposes a regular assessment of the electrode state during measurements. The increase of the signal noise was related to a decrease of the probe capacitance, while the false current density signal was a result of the potential drift between vibrating and reference electrodes. %0 journal article %@ 1040-0397 %A Bouali, A.C.,Bastos, A.C.,Lamaka, S.V.,Serdechnova, M.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2019 %J Electroanalysis %N 11 %P 2290-2298 %R doi:10.1002/elan.201900435 %T Evaporation of Electrolyte During SVET Measurements: The Scale of the Problem and the Solutions %U https://doi.org/10.1002/elan.201900435 11 %X The objective of this work is to investigate the scale of the effect of spontaneous solution evaporation during SVET (Scanning Vibrating Electrode Technique) measurements and demonstrate how it biases the final results. When SVET maps are continuously acquired for more than several hours, the measured currents are smaller than expected. This is attributed to solvent (typically water) evaporation which leads to an increase in solution conductivity over time. If this is not considered when converting the measured potential differences into the local current densities, the SVET results display currents smaller than the true ones. Here, this effect is studied with a platinum disk electrode as source of a constant current and a model corroding system consisting of the AA2024/CFRP galvanic couple. Corrective actions are proposed to mitigate the problem, either in the experimental set-up or as numerical correction. %0 journal article %@ 0947-5117 %A Gießgen, T.,Mittelbach, A.,Höche, D.,Zheludkevich, M.,Kainer, K. %D 2019 %J Materials and Corrosion %N 12 %P 2247-2255 %R doi:10.1002/maco.201911101 %T Enhanced predictive corrosion modeling with implicit corrosion products %U https://doi.org/10.1002/maco.201911101 12 %X An advanced mathematical approach to describe the influence of corrosion products on the corrosion rate is presented here. The related model can be used as input equation for numerical predictive corrosion simulations or simply as an empirical model, to extrapolate experimental data of corrosion tests to longer times and to interpret the physical parameters behind. This semiempirical model assumes that a constant share of the dissolved metal precipitates on the surface and hinders the diffusion processes. Hence, the effective corrosion rate decreases exponentially with increasing dissolution. The explicit corrosion progress over time is derived by time integration on a newly developed, time dependent corrosion rate equation. The derived expression can be effortlessly implemented in existing for example finite element method, which is demonstrated for the uniform corrosion of a zinc surface. Furthermore, this approach is qualitatively compared with other empirical models for corrosion products and the validity is demonstrated by fitting of experimental data. A very good agreement between experiment and theory can be achieved for various materials and environments considering no change of the driving corrosion mechanism. %0 journal article %@ 0169-4332 %A Ofoegbu, S.U.,Yasakau, K.,Kallip, S.,Nogueira, H.I.S.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2019 %J Applied Surface Science %N %P 924-936 %R doi:10.1016/j.apsusc.2019.02.024 %T Modification of carbon fibre reinforced polymer (CFRP) surface with sodium dodecyl sulphate for mitigation of cathodic activity %U https://doi.org/10.1016/j.apsusc.2019.02.024 %X Suppression of electrochemical activity (cathodic activity) on CFRP surface at cathodic potentials consistent with galvanic coupling of CFRP with active metals like aluminium and zinc have been demonstrated by electrochemical treatment of CFRP surface in the presence of sodium dodecyl sulphate (SDS). Modification to the CFRP surface by SDS adsorption was established using electrochemical impedance spectroscopy, cyclic voltammetry, and confocal Raman spectroscopy and atomic force microscopy. Electrochemical test results indicate interaction of SDS with CFRP with persistent effects, manifesting in a sustained suppression of electrochemical activity even after washing the treated CFRP surface. Mitigation of CFRP degradation under cathodic polarization in the presence of SDS and/or after prior exposure to SDS was established from scanning electron microscopy. Based on results obtained herein, plausible mechanisms/configurations involved in SDS interaction(s) with carbon fibre surfaces of the CFRP composite (that most probably account for reduced cathodic activity) were postulated. %0 journal article %@ 0928-4931 %A Santos-Coquillat, A.,Esteban-Lucia, M.,Martinez-Campos, E.,Mohedano, M.,Arrabal, R.,Blawert, C.,Zheludkevich, M.,Matykina, E. %D 2019 %J Materials Science & Engineering C %N %P 110026 %R doi:10.1016/j.msec.2019.110026 %T PEO coatings design for Mg-Ca alloy for cardiovascular stent and bone regeneration applications %U https://doi.org/10.1016/j.msec.2019.110026 %X Four bioactive PEO (plasma electrolytic oxidation) coatings were generated on Mg0.8Ca alloy using a Ca/P-based electrolyte and adding Si or Fas necessary. Surface characteristics, chemical composition and ion liberation of the coatings were characterized using SEM/EDS (Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy), X-ray diffraction, optical profilometry and ICP-OES (inductively coupled plasma optical emission spectrometry). Direct biocompatibility studies were performed by seeding premyoblastic, endothelial and preosteoblastic cell lines over the coatings. Biocompatibility of the coatings was also evaluated with respect to murine endothelial, preosteoblastic, preosteoclastic and premyoblastic cell cultures using extracts obtained by the immersion degradation of the PEO-coated specimens. The coatings reduced the degradation of magnesium alloy and released Mg Ca, P, Si and F. Of all the studied compositions, the Si-containing PEO coating exhibited the optimal characteristics for use in all potential applications, including bone regeneration and cardiovascular applications. Coatings with high F content negatively influenced the endothelial cells. RAW 264.7, MC3T3 and co-culture differentiation studies using extracts of PEO coated Mg0.8Ca demonstrated improved osteoclastogenesis and osteoblastogenesis processes compared to bare alloy. %0 journal article %@ 0010-938X %A Jiang, P.,Blawert, C.,Scharnagl, N.,Zheludkevich, M.L. %D 2019 %J Corrosion Science %N %P 62-73 %R doi:10.1016/j.corsci.2019.03.044 %T Influence of water purity on the corrosion behavior of Mg0.5ZnX (X=Ca, Ge) alloys %U https://doi.org/10.1016/j.corsci.2019.03.044 %X Influence of water purity on the corrosion behavior of as-cast Mg0.5Zn, Mg0.5Zn0.5Ca and Mg0.5Zn0.2Ge alloys was investigated by preparing 0.9 wt.% NaCl solution with deionized and tap water. Mg(OH)2 layer with limited protection ability was predominately formed on the surfaces in solution prepared with deionized water. In contrast, besides the primary Mg(OH)2 layer, different crystals of CaCO3 were formed as a secondary corrosion products layer in solution prepared with tap water, which improved the corrosion resistance of alloys by almost one order of magnitude. Moreover, the crystallographic form of CaCO3 was influenced by the content of calcium in the alloy. %0 journal article %@ 1359-7345 %A Mikhailau, A.,Maltanava, H.,Poznyak, S.K.,Salak, A.N.,Zheludkevich, M.L.,Yasakau, K.A.,Ferreira, M.G.S. %D 2019 %J Chemical Communications : ChemComm %N %P 6878-6881 %R doi:10.1039/C9CC02571E %T One-step synthesis and growth mechanism of nitrate intercalated ZnAl LDH conversion coatings on zinc %U https://doi.org/10.1039/C9CC02571E %X An approach for the synthesis of ZnAl–NO3 LDH conversion coatings on zinc in an aqueous acidic Al(NO3)3/NaNO3 solution is demonstrated for the first time. The growth mechanism has been investigated using time resolved structural, microstructural and analytical methods. A LDH growth model involving both electrochemical and chemical processes is suggested. %0 journal article %@ 2079-6412 %A Han, J.,Blawert, C.,Tang, S.,Yang, J.,Hu, J.,Zheludkevich, M. %D 2019 %J Coatings %N 4 %P 259 %R doi:10.3390/coatings9040259 %T Effect of Surface Pre-Treatments on the Formation and Degradation Behaviour of a Calcium Phosphate Coating on Pure Magnesium %U https://doi.org/10.3390/coatings9040259 4 %X Calcium phosphate (CaPh) coatings are considered promising surface treatments for Mg-based implants. Normally, the phase conversion process of CaPh compounds occurs during immersion in simulated body fluid (SBF) and allows the easy penetration of a corrosive medium. To solve the issue, pre-treatment is often performed, creating an effective barrier that further improves the corrosion resistance of the underlying Mg. In the present work three pre-treatments including hydrothermal treatment, anodization, and plasma electrolytic oxidation (PEO) were performed on pure Mg prior to CaPh deposition. Results indicated that the composition, morphology, and thickness of the CaPh coatings were strongly influenced by the pre-treatments. Dicalcium phosphate dihydrate (DCPD) was formed on PEO surface, whilst DCPD and hydroxyapatite (HA) were deposited on hydrothermally prepared and anodized surfaces. HA could be deposited on the studied samples during immersion in SBF. The electrochemical impedance spectrum indicated that CaPh coating combined with PEO pre-treatment had the highest corrosion resistance at 120 h due to the superior barrier properties conferred by the PEO layer. %0 journal article %@ 0013-4651 %A Oliveira, M.,Bastos, A.,Kallip, S.,Hack, T.,Zheludkevich, M.,Ferreira, M. %D 2019 %J Journal of the Electrochemical Society %N 16 %P 642-648 %R doi:10.1149/2.0761916jes %T Corrosion inhibition and acceleration by rare earth ions in galvanic couples %U https://doi.org/10.1149/2.0761916jes 16 %X Rare earth ions are amongst the most promising new generation corrosion inhibitors. This communication describes conditions where, instead of inhibition, acceleration of corrosion occurs after rare earth salts are added to solution. The work was carried out mainly with the Fe-Zn galvanic couple and different rare earth salts, using electrochemical techniques such as galvanic current measurements, scanning vibrating electrode technique and linear sweep voltammetry (polarization curves). The increased activity in the couple is associated to an unexpected cathodic reaction that is observed after adding the salts to solution. The new reaction signifies supplementary oxidant species being reduced at the iron electrode (cathode), accelerating the oxidation of zinc (anode). The nature of this cathodic process is discussed. %0 journal article %@ 1998-0124 %A Okulov, I.V.,Lamaka, S.V.,Wada, T.,Yubuta, K.,Zheludkevich, M.L.,Weissmueller, J.,Markmann, J.,Kato, H. %D 2018 %J Nano Research %N 12 %P 6428-6435 %R doi:10.1007/s12274-018-2167-9 %T Nanoporous magnesium %U https://doi.org/10.1007/s12274-018-2167-9 12 %X In this study, we present freestanding nanoporous magnesium as a novel lightweight material with high potential for structural and functional applications. Thus far, the high reactivity of Mg with oxygen and aqueous media prevented the fabrication of nanoporous Mg. First, in order to synthesize nanoporous Mg, we fabricated a bicontinuous nanocomposite consisting of interpenetrating Mg and non-Mg phases by liquid metal dealloying. The non-Mg phases in the nanocomposite protect Mg against corrosion. Second, we etched the non-Mg phases from the nanocomposite, leaving nanoporous Mg, using HF solution. This process is advantageous because the nanoporous Mg was passivated by a MgF2 layer during the etching. Our approach is very flexible, and we demonstrate that versatile microstructures of the nanoporous Mg—e.g., nanoscale bicontinuous network, hierarchical, or plate-like structures—can be designed for the given needs. More importantly, these nanoporous Mg samples can readily be exposed to air without being harmed by corrosion. %0 journal article %@ 2191-1363 %A Silva, E.L.,Lamaka, S.V.,Mei, D.,Zheludkevich, M.L. %D 2018 %J ChemistryOPEN %N 8 %P 664-668 %R doi:10.1002/open.201800076 %T The Reduction of Dissolved Oxygen During Magnesium Corrosion %U https://doi.org/10.1002/open.201800076 8 %X The consumption of dissolved oxygen (DO) during the corrosion of commercially pure magnesium specimens was investigated by localized corrosion techniques. The concentration of oxygen and the local current density on the near‐surface of magnesium were measured simultaneously by a micro‐optode DO sensor and the scanning vibrating electrode technique (SVET), respectively. Diamond microelectrodes were also used for DO mapping. Significant DO depletion was found since the initial immersion time of Mg in NaCl 0.5 m, and a correlation could be established between DO consumption and areas of anodic and cathodic activity. These findings assume particular relevance for the corrosion of Mg alloys or magnesium components with impurity levels higher than the tolerance limit. Moreover, this study points out the significance of the partial oxygen pressure as an influential parameter during magnesium corrosion. %0 journal article %@ 0010-938X %A Yang, J.,Blawert, C.,Lamaka, S.V.,Yasakau, K.A.,Wang, L.,Laipple, D.,Schieda, M.,Di, S.,Zheludkevich, M.L. %D 2018 %J Corrosion Science %N %P 222-237 %R doi:10.1016/j.corsci.2018.07.027 %T Corrosion inhibition of pure Mg containing a high level of iron impurity in pH neutral NaCl solution %U https://doi.org/10.1016/j.corsci.2018.07.027 %X Three sodium salts of organic acids (2,5-pyridinedicarboxylic, 3-methylsalicylic and fumaric) were studied as corrosion inhibitors for pure magnesium containing a high level (342 ppm) of Fe impurity. The inhibition effect of the three inhibitors was evaluated by means of hydrogen evolution, electrochemical and surface analysis techniques. Significant reduction in corrosion rate was revealed for of the tested inhibitors in pH neutral NaCl electrolyte. 2,5-pyridinedicarboxylate and fumarate showed the effects characteristic for mixed-type inhibitors, while 3-methylsalicylate performed more as cathodic inhibitor, complying with the iron re-deposition model, where the electrochemical activity of iron-rich particles was effectively inhibited. %0 journal article %@ 0010-938X %A Yang, J.,Blawert, C.,Lamaka, S.V.,Snihirova, D.,Lu, X.,Di, S.,Zheludkevich, M.L. %D 2018 %J Corrosion Science %N %P 99-110 %R doi:10.1016/j.corsci.2018.06.014 %T Corrosion protection properties of inhibitor containing hybrid PEO-epoxy coating on magnesium %U https://doi.org/10.1016/j.corsci.2018.06.014 %X A hybrid PEO-epoxy coating was developed for magnesium. A highly-efficient corrosion inhibitor (3-methysalicylate) was impregnated into the anodized layer, which was sealed by an epoxy layer through dip-coating process. Influence of dip-coating parameters on coating properties was investigated. The corrosion performance was evaluated through general and localized electrochemical techniques. As a result, the epoxy layers registered superior resistance, whereas the anodized layer suppressed corrosion expansion. Longer immersion and triple-dipping favored the production of better sealed epoxy layer. The active protection mechanism was achieved by suppression the re-deposition of detrimental impurity and/or adsorption upon the exposed surface from incorporated inhibitor. %0 journal article %@ 0378-7753 %A Deng, M.,Hoeche, D.,Lamaka, S.V.,Snihirova, D.,Zheludkevich, M.L. %D 2018 %J Journal of Power Sources %N %P 109-118 %R doi:10.1016/j.jpowsour.2018.05.090 %T Mg-Ca binary alloys as anodes for primary Mg-air batteries %U https://doi.org/10.1016/j.jpowsour.2018.05.090 %X In this research, Mg-Ca binary alloys are evaluated as anode material candidates for primary Mg-air batteries. The effect of Ca content on self-corrosion and discharge performance of Mg anode is investigated through microstructure characterization, electrochemical measurements and half-cell discharge tests. Then the composition of Mg-Ca alloys is optimized in terms of reduced self-corrosion and improved discharge performance. The basic characteristics of Mg-air batteries with optimized Mg-Ca alloy as anode are tested and compared to those based on high purity Mg and defined commercial Mg alloys. The results show that Mg-0.1 wt. % Ca alloy has the best self-corrosion behavior and discharge performance among all prepared Mg-Ca alloys. The Mg-air battery with Mg-0.1 wt. % Ca alloy as anode offers higher cell voltage and specific energy than those based on high purity Mg, AM50 and AZ31 alloys. %0 journal article %@ 2045-2322 %A Hoeche, D.,Lamaka, S.V.,Vaghefinazari, B.,Braun, T.,Petrauskas, R.P.,Fichtner, M.,Zheludkevich, M.L. %D 2018 %J Scientific Reports %N %P 7578 %R doi:10.1038/s41598-018-25789-8 %T Performance boost for primary magnesium cells using iron complexing agents as electrolyte additives %U https://doi.org/10.1038/s41598-018-25789-8 %X Aqueous Mg battery technology holds significant appeal, owing to the availability of raw materials, high power densities and the possibility of fast mechanical recharge. However, Mg batteries have so far been prone to decreased capacity due to self-corrosion of the anodes from the electrochemical redeposition of impurities, such as Fe, which results in parasitic cathodically active sites on the discharging anode. This work demonstrates that by adding Fe3+-complexing agents like Tiron or salicylate to the aqueous electrolyte of an Mg battery, it was possible to prevent the redeposition of Fe impurities and subsequent self-corrosion of the anode surface, thereby boosting battery performance. To prevent detrimental fouling of anode surface by Mg(OH)2, employed Fe3+-complexing agents must also form soluble complexes with Mg2+ of moderate stability. The interplay of these requirements predetermines the improvement of operating voltage and utilization efficiency. %0 journal article %@ 1996-1944 %A Serdechnova, M.,Karpushenkov, S.A.,Karpushenkava, L.S.,Starykevich, M.,Ferreira, M.G.S.,Hack, T.,Iuzviuk, M.H.,Zobkalo, I.A.,Blawert, C.,Zheludkevich, M.L. %D 2018 %J Materials %N 12 %P 2428 %R doi:10.3390/ma11122428 %T The Influence of PSA Pre-Anodization of AA2024 on PEO Coating Formation: Composition, Microstructure, Corrosion, and Wear Behaviors %U https://doi.org/10.3390/ma11122428 12 %X In the frame of the current work, it was shown that plasma electrolytic oxidation (PEO) treatment can be applied on top of phosphoric sulfuric acid (PSA) anodized aluminum alloy AA2024. Being hard and well-adherent to the substrate, PEO layers improve both corrosion and wear resistance of the material. To facilitate PEO formation and achieve a dense layer, the systematic analysis of PEO layer formation on the preliminary PSA anodized layer was performed in this work. The microstructure, morphology, and composition of formed PEO coatings were investigated using scanning electron microscopy (SEM), x-ray diffraction (XRD), and glow-discharge optical emission spectroscopy (GDOES). It was shown that under constant current treatment conditions, the PSA layer survived under the applied voltage of 350 V, whilst 400 V was an intermediate stage; and under 450 V, the PSA layer was fully converted after 5 min of the treatment. The comparison test with PEO formation on the bare material was performed. It was confirmed that during the “sparking” mode (400 V) of PEO formation, the PEO coatings, formed on PSA treated AA2024, were more wear resistant than the same PEO coatings on bare AA2024. %0 journal article %@ 0010-938X %A Mata, D.,Scharnagl, N.,Lamaka, S.V.,Malheiro, E.,Maia, F.,Zheludkevich, M.L. %D 2018 %J Corrosion Science %N %P 307-320 %R doi:10.1016/j.corsci.2018.05.034 %T Validating the early corrosion sensing functionality in poly (ether imide) coatings for enhanced protection of magnesium alloy AZ31 %U https://doi.org/10.1016/j.corsci.2018.05.034 %X This work reports on the validation studies of early corrosion sensing poly ether imide (PEI) coatings with incorporated pH-sensing phenolphthalein loaded silica nano-sized capsules (SiNCs-PhPh) on AZ31 magnesium alloys. Immersion and drop tests validated the high sensing accuracy and PhPh color-signaling reproducibility of the coatings upon onset of corrosion. This behavior is correlated to the homogeneous dispersion of SiNC particle agglomerates confirmed by 3D Raman mapping and SEM analysis. Complementary differential video imaging technique (DVIT) assisted by electrochemical impedance spectroscopy (EIS) investigations provided clues for a good correlation between the kinetics of color signaling and the corrosion activity. Mechanistic insights into the pH-sensing/color-signaling functionality in PEI coatings are suggested. %0 journal article %@ 2045-2322 %A Shulha, T.N.,Serdechnova, M.,Lamaka, S.V.,Wieland, D.C.F.,Lapko, K.N.,Zheludkevich, M. %D 2018 %J Scientific Reports %N %P 16409 %R doi:10.1038/s41598-018-34751-7 %T Chelating agent-assisted in situ LDH growth on the surface of magnesium alloy %U https://doi.org/10.1038/s41598-018-34751-7 %X In situ formation of layered double hydroxides (LDH) on metallic surfaces has recently been considered a promising approach for protective conversion surface treatments for Al and Mg alloys. In the case of Mg-based substrates, the formation of LDH on the metal surface is normally performed in autoclave at high temperature (between 130 and 170 °C) and elevated pressure conditions. This hampers the industrial application of MgAl LDH to magnesium substrates. In this paper, the growth of MgAl LDH conversion coating directly on magnesium alloy AZ91 at ambient conditions (25 °C) or elevated temperatures is reported in carbonate free electrolyte for the first time. The direct LDH synthesis on Mg alloys is enabled by the presence of organic chelating agents (NTA and EDTA), which control the amount of free and/or hydroxyl bound Mg2+ and Al3+ in the solution. The application of the chelating agents help overcoming the typical technological limitations of direct LDH synthesis on Mg alloys. The selection of chelators and the optimization of the LDH treatment process are supported by the analysis of the thermodynamic chemical equilibria. %0 journal article %@ 1944-8244 %A Yang, J.,Di, S.,Blawert, C.,Lamaka, S.V.,Wang, L.,Fu, B.,Jiang, P.,Zheludkevich, M.L. %D 2018 %J ACS Applied Materials and Interfaces %N 36 %P 30741-30751 %R doi:10.1021/acsami.8b10612 %T Enhanced Wear Performance of Hybrid Epoxy-Ceramic Coatings on Magnesium Substrates %U https://doi.org/10.1021/acsami.8b10612 36 %X Epoxy-based polymer was deposited as sealing agent on porous anodized coatings prepared by plasma electrolytic oxidation (PEO) to construct multilayered “soft-hard” coatings on Mg substrates. Different thicknesses and microstructures of the top epoxy layer were achieved by employing different dip-coating strategies. Atomic force microscopy, pull-off tests, and nanoindentation tests were conducted to study the surface roughness, the adhesion strength of the epoxy layer, and the mechanical properties of each component in the hybrid coating system. The micropores and other defects on the anodized layers were sealed by the epoxy polymer, which decreased the surface roughness. The dominant abrasive wear behavior of blank PEO coatings was significantly reduced by the epoxy layers, and the wear mechanism of the hybrid coatings was proposed considering both the microstructure of the hybrid coatings and the mechanical properties of the different components in the hybrid system. %0 journal article %@ 2079-6412 %A Lu, X.,Chen, Y.,Blawert, C.,Li, Y.,Zhang, T.,Wang, F.,Kainer, K.U.,Zheludkevich, M.L. %D 2018 %J Coatings %N 9 %P 306 %R doi:10.3390/coatings8090306 %T Influence of SiO2 Particles on the Corrosion and Wear Resistance of Plasma Electrolytic Oxidation-Coated AM50 Mg Alloy %U https://doi.org/10.3390/coatings8090306 9 %X The influence of SiO2 particles on the microstructure, phase composition, corrosion and wear performance of plasma electrolytic oxidation (PEO) coatings on AM50 Mg was investigated. Different treatment durations were applied to fabricate coatings in an alkaline, phosphate-based electrolyte (1 g/L KOH + 20 g/L Na3PO4 + 5 g/L SiO2), aiming to control the incorporated amount of SiO2 particles in the layer. It was found that the uptake of particles was accompanied by the coating growth at the initial stage, while the particle content remained unchanged at the final stage, which is dissimilar to the evolution of the coating thickness. The incorporation mode of the particles and phase composition of the layer was not affected by the treatment duration under the voltage-control regime. The corrosion performance of the coating mainly depends on the barrier property of the inner layer, while wear resistance primarily relies on the coating thickness. %0 journal article %@ 0257-8972 %A Lu, X.,Blawert, C.,Kainer, K.U.,Zhang, T.,Wang, F.,Zheludkevich, M.L. %D 2018 %J Surface and Coatings Technology %N %P 1-14 %R doi:10.1016/j.surfcoat.2018.08.003 %T Influence of particle additions on corrosion and wear resistance of plasma electrolytic oxidation coatings on Mg alloy %U https://doi.org/10.1016/j.surfcoat.2018.08.003 %X The influence of particles with different melting points on the microstructure, phase composition and properties of plasma electrolytic oxidation (PEO) coatings was investigated. PEO coatings were produced on AM50 Mg alloy from an alkaline phosphate-based electrolyte (1 g/L KOH + 20 g/L Na3PO4) with and without addition of clay, SiO2, Si3Ni4 and SiC micro-sized particles. The incorporation mode of the particles primarily depends on their melting point. Particles with relatively low melting point can achieve fully reactive incorporation, while high melting point particles are mainly inertly incorporated into the coating. Reactive incorporation of clay particles contributes to formation of a dense layer and improvement of corrosion and wear resistance. Addition of SiO2 and Si3Ni4 particles can improve the wear resistance of PEO coating, while the corrosion performance and degradation process of the coating is marginally influenced by the inertly incorporated particles. %0 journal article %@ 1432-8488 %A Lisenkov, A.D.,Poznyak, S.K.,Almeida, C.M.R.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2018 %J Journal of Solid State Electrochemistry %N 12 %P 3913-3920 %R doi:10.1007/s10008-018-4083-z %T Encapsulation of Al and Ti-Al alloy 1-D nanorods into oxide matrix by powerful pulsed discharge method %U https://doi.org/10.1007/s10008-018-4083-z 12 %X Encapsulated metal nanostructures were prepared using the powerful pulsed discharge method. Metal nanorods were obtained in porous titania and alumina matrix by direct electrodeposition from 1-ethyl-3-methylimidazolium chloride-based ionic liquids. The deposition process was characterized by cyclic voltammetry. Morphology of the encapsulated structures was studied by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) for morphological and elemental analysis. It was found that the most efficient method for electrodeposition of pure aluminum into titania nanotubes is the potential cycling method, while for deposition of the Al-Ti alloy in alumina pores a pulsed method with three different steps is preferable. Closing the titania nanotubes was found to be possible both with empty and metal-filled pores, whereas in alumina matrix this procedure can be performed only when pores are filled with a conductive material. The obtained results throw light on the mechanism of porous film encapsulation under high-voltage pulses and allow preparing encapsulated nanostructures in the oxide films. %0 journal article %@ 0010-938X %A Zadeh, M.A.,Tedim, J.,Zheludkevich, M.L.,Zwaag, S.van der,Garcia, S.J. %D 2018 %J Corrosion Science %N %P 35-45 %R doi:10.1016/j.corsci.2018.02.018 %T Synergetic active corrosion protection of AA2024-T3 by 2D- anionic and 3D-cationic nanocontainers loaded with Ce and mercaptobenzothiazole %U https://doi.org/10.1016/j.corsci.2018.02.018 %X In the current paper the corrosion inhibition synergy between Ce3+ loaded NaY-zeolite (NaY-Ce) and 2-Mercaptobenzothiazole (MBT) loaded Zn-Al layered double hydroxide (LDH-MBT) containers is presented. Solutions and water-borne epoxy coatings containing different ratios of the two loaded carriers were prepared and their protection of AA2024-T3 and damaged coatings characterized using global and local electrochemical techniques and other complementary tools. The coatings containing container-combinations showed exceptional corrosion protection over a broad range of NaY-Ce:LDH-MBT weight ratios, with 90:10 being the optimal. The current work landmarks the need for synergetic inhibiting studies devoted to carrier-inhibitor systems in coatings. %0 journal article %@ 0257-8972 %A Chen, Y.,Lu, X.,Blawert, C.,Zheludkevich, M.L.,Zhang, T.,Wang, F. %D 2018 %J Surface and Coatings Technology %N %P 379-388 %R doi:10.1016/j.surfcoat.2018.01.022 %T Formation of self-lubricating PEO coating via in-situ incorporation of PTFE particles %U https://doi.org/10.1016/j.surfcoat.2018.01.022 %X Self-lubricating plasma electrolytic oxidation (PEO) coatings have been fabricated on AZ91 magnesium alloy via in-situ incorporation of PTFE particles. Surfactants are used to improve dispersion stability of the particles in aqueous solution and relatively low energy input is applied to ensure the particles are inertly incorporated into the coating. It was found that the porous layer has been sealed significantly and PTFE-enriched ridge-like protrusions can be obtained on the coating surface after sufficient treatment time. 3D surface micro-topography was reconstructed to disclose the uptake of the particles and wear mechanisms of the coatings. The particle-containing protrusions can act as lubricant reservoirs, leading to ultra-low and stable friction coefficient between the coating and its counterpart during entire dry sliding wear test. The formation of the ridge-like protrusions is related to micro-sized gas bubbles adherence to the coating surface due to high viscosity of the electrolyte. As a consequence, the intensity of electric field at the edge of the bubbles increases, which could facilitate rapid sintering and accumulation of PTFE particles at the electrolyte/gas/coating interface. %0 journal article %@ 0257-8972 %A Hakimizad, A.,Raeissi, K.,Golozar, M.A.,Lu, X.,Blawert, C.,Zheludkevich, M.L. %D 2018 %J Surface and Coatings Technology %N %P 210-221 %R doi:10.1016/j.surfcoat.2018.02.042 %T Influence of cathodic duty cycle on the properties of tungsten containing Al2O3/TiO2 PEO nano-composite coatings %U https://doi.org/10.1016/j.surfcoat.2018.02.042 %X Current waveforms with different cathodic duty cycles of 0, 20 and 40% were applied to coat 7075 aluminum alloy in a silicate based electrolyte containing titania nano-particles. Using a constant current mode, the recorded voltage-time response showed that the required voltage for PEO coating process is lower in the presence of sodium tungstate as additive. By increasing the cathodic duty cycle, pancake surface morphology was converted to crater-like. Phase and chemical composition of the coatings were investigated by using grazing angle XRD and SEM/EDS. The tungsten concentration decreased linearly with the increase of cathodic duty cycle, which is dissimilar to the titania content. It was proposed that physical entrapping has been associated with electrophoretic incorporation of titania nano-particles, while the adsorption mechanism of tungstate anions is purely electrophoretic. Corrosion performance of the coatings was evaluated by potentiodynamic polarization and EIS measurements. Addition of sodium tungstate was detrimental for corrosion performance of the coating in the case of unipolar waveform while the corrosion resistance was improved when bipolar waveforms were used. Long-term corrosion behavior of the coatings was investigated by EIS up to 16 weeks. The results showed remarkable difference between corrosion performance of the coatings produced by unipolar and bipolar waveforms, but the difference was negligible for the coatings produced by the bipolar waveforms with different cathodic duty ratios. %0 journal article %@ 0010-938X %A Lu, X.,Blawert, C.,Tolnai, D.,Subroto, T.,Kainer, K.U.,Zhang, T.,Wang, F.,Zheludkevich, M.L. %D 2018 %J Corrosion Science %N %P 395-402 %R doi:10.1016/j.corsci.2018.05.019 %T 3D reconstruction of plasma electrolytic oxidation coatings on Mg alloy via synchrotron radiation tomography %U https://doi.org/10.1016/j.corsci.2018.05.019 %X Plasma electrolytic oxidation (PEO) is a well-known surface treatment for Mg alloys, while high porosity is an issue to achieve long-term corrosion protection. Nevertheless, the presence of inherent porosity can be turned into advantage while used as nano/micro-structured reservoir of corrosion inhibitors or functional agents next to Mg surface providing an active corrosion protection and multi-functionality. For the first time, we report here the 3D internal architecture of PEO coated Mg via synchrotron-based microtomography. The pore characteristics have been qualitatively and quantitatively investigated to unveil the formation of the coating porosity and potential incorporation of functional elements in the pores. %0 journal article %@ 0010-938X %A Yasakau, K.A.,Kuznetsova, A.,Kallip, S.,Starykevich, M.,Tedim, J.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2018 %J Corrosion Science %N %P 299-313 %R doi:10.1016/j.corsci.2018.08.039 %T A novel bilayer system comprising LDH conversion layer and sol-gel coating for active corrosion protection of AA2024 %U https://doi.org/10.1016/j.corsci.2018.08.039 %X In this work active corrosion protection of AA2024 by a bilayer system consisting of a LDH (layered double hydroxides) conversion layer coated by a sol-gel film was studied. Impedance and Scanning vibrating electrode technique (SVET) studies demonstrated an efficient active corrosion protection and self-healing abilities of the systems containing LDH layer loaded with vanadate corrosion inhibitor. Microstructural and chemical analysis of the surface after corrosion testing showed accumulation of chlorine signal in LDH coatings. The scavenging of chlorides and release of vanadate inhibitor from LDH can explain high efficiency of corrosion inhibition of AA2024 by the novel protective system. %0 journal article %@ 2305-6894 %A Chirkunov, A.A.,Zheludkevich, M.L. %D 2018 %J International Journal of Corrosion and Scale Inhibition %N 3 %P 376-389 %R doi:10.17675/2305-6894-2018-7-3-8 %T Corrosion inhibition of Elektron WE43 magnesium alloy in NaCl solution %U https://doi.org/10.17675/2305-6894-2018-7-3-8 3 %X Magnesium alloys have a wide range of applications but suffer low corrosion resistance. One of the most accessible ways to protect metals from corrosion, which can also be combined with other methods, is the use of corrosion inhibitors. The effect of 1,2,3-benzotriazole, 5-chloro-1,2,3-benzotriazole and sodium dioctyl phosphate on the corrosion of Elektron WE43 magnesium alloy in 0.05 M NaCl solution was studied using polarization and EIS measurements. Azoles do not exhibit the inhibitive action towards the WE43 alloy, but they slightly reduce the barrier effect of the film of corrosion products. Sodium dioctyl phosphate (DOP) is an effective inhibitor due to its anionic nature. It mainly inhibits the anodic dissolution of the alloy and has a slight effect on the cathodic process. DOP enhances the protective effect in time due to improvement of protective films. An increase in DOP concentration depresses the anodic dissolution of the alloy as well as the local depassivation, which is characterized by a displacement of the pitting potential in the positive direction. Scanning vibrating electrode technique (SVET) measurements confirmed the effectiveness of DOP as a corrosion inhibitor for Electron WE43 alloy. %0 journal article %@ 0257-8972 %A Ma, X.,Blawert, C.,Hoeche, D.,Kainer, K.U.,Zheludkevich, M.L. %D 2018 %J Surface and Coatings Technology %N %P 281-297 %R doi:10.1016/j.surfcoat.2018.07.024 %T Simulation assisted investigation of substrate geometry impact on PEO coating formation %U https://doi.org/10.1016/j.surfcoat.2018.07.024 %X Plasma electrolytic oxidation (PEO) technology is widely used for coating of light metals and their alloys because of the excellent coating properties it provides and its non-line-of-sight treatment which allows forming coatings on substrates with complex geometry. However, non-uniform coating thickness and surface properties may be an issue at different locations on substrates with complex shapes. In order to understand the effect of substrate geometry on PEO coating formation and uniformity, AM50 magnesium alloy specimens with drill holes of various diameter to length ratios were coated. PEO coatings were applied on these substrates in an alkaline electrolyte at constant voltage. Phase composition, coating morphology, thickness and elements distribution were studied at different locations of the drill holes. Complementary, a 3D model describing the processing is built to simulate and to predict the effect of substrate geometry on the anodic current distribution and coating formation using finite element analyses. The model can provide useful information for predicting coating growth and uniformity towards optimized PEO process design. %0 journal article %@ 0933-5137 %A Silva, E.L.,Hoeche, D.,Bouali, A.C.,Serdechnova, M.,Sesenes, R.L.,Scholz, C.S.,Zheludkevich, M.L. %D 2017 %J Materials Science and Engineering Technology - Materialwissenschaft und Werkstofftechnik %N 6 %P 529-545 %R doi:10.1002/mawe.201600702 %T Digital modelling of the galvanic corrosion behaviour of a self–piercing riveted AZ31 - AA5083 hybrid joint - Digitale Modellierung galvanischer Korrosion an stanzgenieteten AZ31-AA5083 Hybridverbunden %U https://doi.org/10.1002/mawe.201600702 6 %X This study focuses on the corrosion phenomena occurring between aluminium AA5083 and AZ31 magnesium sheets, joined with a coated steel self-piercing rivet, by punch rivet technology. These assemblies were studied by immersion tests and scanning vibrating electrode technique (SVET) in sodium chloride solutions, in order to evaluate the effects of joint geometry on corrosion resistance. The observed results were also used for validation of transient finite element method (FEM) simulations. A fully coupled continuum model was used to compute the evolution of electrochemically and chemically induced corrosion attack, formation of corrosion products and their influence on the overall system kinetics. Additionally, X-ray diffraction (XRD) analysis of the corrosion products provided evidence for the formation of layered double hydroxides (LDH), which is in accordance with the model outputs. The current study targets the optimization of joint setup for corrosion resistance. The suitability of corrosion simulation for the AZ31-AA5083-Almac ternary galvanic system is shown alongside. The developed modelling approach represents a step forward in terms of digital service-life assessment of multi-material joints.,Diese Studie untersucht Korrosion an mittels Almac-beschichteten Stanznieten gefügten Aluminium AA5083 Blechen mit Magnesium AZ31. Getestet wird das Korrosionsverhalten der Halbzeuge im Immersionstest (0,5 % NaCl). Zudem wird mittels Scanning Vibrating Electrode Technique in 50 mM NaCl Lösung die Veränderung des Korrosionsstroms aufgrund geänderter Fügeparameter analysiert. Die gemessenen Ergebnisse werden genutzt, um ein transientes Korrosionsmodell (FEM) zu validieren. Dieses gekoppelte Modell beschreibt die elektrochemische als auch chemische Interaktion im System und beschreibt zusätzlich den Einfluss der Korrosionsprodukte auf die Korrosionskinetik. Durch Röntgendiffraktometrie (XRD) Analysen wird gezeigt, dass sich sogenannte Layered Double Hydroxides (LDH) bilden, was wiederum vom Modell abgeleitet werden kann. Der Ansatz kann genutzt werden, um eine Fügung möglichst korrosionsresistent auszulegen. Die Möglichkeit einer digitalen Vorhersage von Korrosion an einem ternären System wie AA5083-AZ31-Almac wird gezeigt. Das Modell bildet daher einen wichtigen Schritt, hin zur rechnerunterstützen Konstruktion (CAE) im Sinne von Lebensdauer und Wartung für hybride Materialverbunde. %0 journal article %@ 0010-9312 %A Yasakau, K.A.,Hoeche, D.,Lamaka, S.L.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2017 %J Corrosion %N 5 %P 583-595 %R doi:10.5006/2260 %T Kelvin Microprobe Analytics on Iron-Enriched Corroded Magnesium Surface %U https://doi.org/10.5006/2260 5 %X This work contributes to the better understanding of Kelvin microprobe response to iron re-deposition related surface morphology changes resulting from Mg corrosion caused by iron-rich impurities. Scanning Kelvin probe force microscopy (SKPFM) was performed on polished Mg samples at well-defined surface conditions occurring from corrosive exposure to 0.05 M NaCl electrolyte or dissolved FeCl2. Volta potential difference was measured and mapped across iron-rich areas, unaffected areas of α-Mg, and on FeCl2 exposed areas. Afterward, the obtained potential values were evaluated via the derived mathematical expression, based on model assumptions. Subsequently, they were compared and then correlated to the corrosion process. %0 journal article %@ 1463-9076 %A Ofoegbu, S.U.,Galvao, T.L.P.,Gomes, J.R.B.,Tedim, J.,Nogueira, H.I.S.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2017 %J Physical Chemistry Chemical Physics %N 8 %P 6113-6129 %R doi:10.1039/C7CP00241F %T Corrosion inhibition of copper in aqueous chloride solution by 1H-1,2,3-triazole and 1,2,4-triazole and their combinations: electrochemical, Raman and theoretical studies %U https://doi.org/10.1039/C7CP00241F 8 %X Triazoles are well-known organic corrosion inhibitors of copper. 1H-1,2,3-Triazole and 1,2,4-triazole, two very simple molecules with the only difference being the positions of the nitrogen atoms in the triazole ring, were studied in this work as corrosion inhibitors of copper in 50 mM NaCl solution using a set of electrochemical and analytical techniques. The results of electrochemical tests indicate that 1H-1,2,3-triazole exhibited superior inhibitor properties but could not suppress anodic copper dissolution at moderate anodic potentials (>+300 mV SCE), while 1,2,4-triazole, although it exhibited higher anodic currents, suppressed anodic copper dissolution at very anodic potentials. Density functional theory calculations were also performed to interpret the measured data and trends observed in the electrochemical studies. The computational studies considered either the inhibitors isolated in the gaseous phase or adsorbed onto Cu(111) surface models. From the calculations, the mechanisms of the inhibitive effects of both triazoles were established and plausible mechanisms of formation of the protective films on the Cu surface were proposed. The results of this study hold positive implications for research in the areas of catalysis, and copper content control in water purification systems. %0 journal article %@ 0257-8972 %A Mohedano, M.,Luthringer, B.J.C.,Mingo, B.,Feyerabend, F.,Arrabal, R.,Sanchez-Egido, P.J.,Blawert, C.,Willumeit-Roemer, R.,Zheludkevich, M.L.,Matykina, E. %D 2017 %J Surface and Coatings Technology %N %P 454-467 %R doi:10.1016/j.surfcoat.2017.02.050 %T Bioactive plasma electrolytic oxidation coatings on Mg-Ca alloy to control degradation behaviour %U https://doi.org/10.1016/j.surfcoat.2017.02.050 %X The present work reports on PEO coatings which can be potentially used for degradation control of Mg-based implant materials. Three coatings were developed on Mg-0.8wt%Ca alloy: two in an electrolyte with fluoride species using different treatment times and one in a fluoride-free electrolyte. Uncoated and coated materials were examined in terms of structure and morphology using TEM, SEM and XRD. The corrosion investigations on fluoride-containing samples were performed using DC potentiodynamic curves, EIS and hydrogen evolution measurements. Both PEO coatings improved the corrosion resistance compared to the bulk material and the best behaviour was found for the thinnest PEO coating (PEO1-F). The amount of released F− ions was also measured with the aim of underpinning the effect of coatings and presence of fluorides species on the cell response. The bulk material and the coated alloy were studied using live/dead cell test, with the best results obtained for thinner fluoride containing coatings. %0 journal article %@ 0010-938X %A Lamaka, S.V.,Vaghefinazari, B.,Mei, D.,Petrauskas, R.P.,Hoeche, D.,Zheludkevich, M-L. %D 2017 %J Corrosion Science %N %P 224-240 %R doi:10.1016/j.corsci.2017.07.011 %T Comprehensive screening of Mg corrosion inhibitors %U https://doi.org/10.1016/j.corsci.2017.07.011 %X This work presents the results of a systematic screening for magnesium corrosion inhibitors. The ability to form stable soluble complexes with Feii/iii was considered on first place when choosing the compounds for hydrogen evolution tests. Inhibiting effect of 151 individual compounds was tested towards six alloys (AZ31, AZ91, AM50, WE43, ZE41 and Elektron 21) and three grades of pure magnesium. Newly identified and previously reported inhibitors are ranked by their inhibiting efficiency and compared with Cr (VI) reference. A number of new inhibitors are discovered with efficiency exceeding that of chromate. %0 journal article %@ 1932-7447 %A Galvao, T.L.P.,Neves, C.S.,Zheludkevich, M.L.,Gomes, J.R.B.,Tedim, J.,Ferreira, M.G.S. %D 2017 %J The Journal of Physical Chemistry C %N 4 %P 2211-2220 %R doi:10.1021/acs.jpcc.6b10860 %T How Density Functional Theory Surface Energies May Explain the Morphology of Particles, Nanosheets, and Conversion Films Based on Layered Double Hydroxides %U https://doi.org/10.1021/acs.jpcc.6b10860 4 %X Conversion films based on layered double hydroxides constitute an important and environmentally friendly technology for the corrosion protection of aeronautical structures. Unfortunately, the morphology of layered double hydroxide (LDH) conversion films is still not well understood. In the present work, the structure and driving forces behind the morphology of zinc–aluminum LDH conversion films on aluminum alloy 2024 (AA2024) are explained from the perspective of molecular modeling. Since LDH particles are the core structures of LDH conversion films, the first step in this work was to understand the relation between structure and morphology of the particles themselves and the single-layer nanosheets that constitute them. Results regarding LDH’s crystallites, particles, and conversion films obtained using X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are interpreted using periodic model density functional theory (DFT) calculations. On the basis of the understanding of the formation of LDH particles and their exfoliation to obtain single-layer nanosheets, for the first time, LDH conversion films have been modeled using periodic model DFT. The results point to a preferential orientation of the cationic layers perpendicular to the surface, thus explaining the film morphology (SEM and AFM) and providing a rational for their crystallization process. %0 journal article %@ 0261-3069 %A Mohedano, M.,Serdechnova, M.,Starykevich, M.,Karpushenkov, S.,Bouali, A.C.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2017 %J Materials and Design %N %P 36-46 %R doi:10.1016/j.matdes.2017.01.097 %T Active protective PEO coatings on AA2024: Role of voltage on in-situ LDH growth %U https://doi.org/10.1016/j.matdes.2017.01.097 %X Four voltage-controlled plasma electrolytic oxidation (PEO) coatings were developed on AA2024 aluminum alloy at 350 V, 400 V, 450 V and 500 V. Zn–Al LDH layer was in situ grown and loaded with corrosion inhibitor (vanadate) on the coatings to provide active protection to the PEO layers. The structure, morphology and composition of PEO coatings without and with LDH-NO3 and LDH-VOx were investigated using SEM, EDS, XRD and GDOES. Coatings formed at higher voltages (thicker and more stable) reveal a decrease of LDH flakes on the surface. The corrosion behavior and the effectiveness of LDH formation and inhibitor intercalation were also studied. Electrochemical impedance spectroscopy and scanning vibrating electrode techniques have shown a remarkable increase in the corrosion resistance of the LDH-inhibitor treated sample in comparison with PEO coated AA2024 specimen. %0 journal article %@ 0947-5117 %A Klein, M.,Lu, X.,Blawert, C.,Kainer, K.U.,Zheludkevich, M.L.,Walther, F. %D 2017 %J Materials and Corrosion %N 1 %P 50-57 %R doi:10.1002/maco.201609088 %T Influence of plasma electrolytic oxidation coatings on fatigue performance of AZ31 Mg alloy %U https://doi.org/10.1002/maco.201609088 1 %X Magnesium and its alloys are attractive for lightweight construction, but suffer often from poor corrosion resistance. Plasma electrolytic oxidation is a promising surface treatment to overcome these limitations. Recently, introduction of particles to the PEO electrolyte has been explored as new strategy to provide a wider range of compositions and new functionalities for PEO coatings. However, this surface treatment can have negative impact on the fatigue strength. In the present study, the influence of PEO coatings with and without particle addition on the corrosion fatigue behavior of AZ31 Mg alloy is investigated. The corrosion fatigue behavior is investigated in load increase tests and constant amplitude tests in 0.5% NaCl solutions. Results are correlated with the corrosion behavior evaluated in polarization and electrochemical impedance spectroscopy measurements. Corrosion tests show significant improvement of the corrosion resistances of PEO-coated specimens. However, the uncoated material exhibits the highest corrosion fatigue strength, whereas a reduction of 7% for the PEO-coated specimen without particles and 27% for the PEO-coated specimen with particles is found. %0 journal article %@ 2196-7350 %A Silva, E.L.,Mishra, Y.K.,Fernandes, A.J.S.,Silva, R.F.,Strobel, J.,Kienle, L.,Adelung, R.,Oliveira, F.J.,Zheludkevich, M.L. %D 2017 %J Advanced Materials Interfaces %N 10 %P 1700019 %R doi:10.1002/admi.201700019 %T Direct Synthesis of Electrowettable Carbon Nanowall–Diamond Hybrid Materials from Sacrificial Ceramic Templates Using HFCVD %U https://doi.org/10.1002/admi.201700019 10 %X Carbon‐on‐carbon materials carry the potential to be a major disruptive technology in fields like energy storage and electronics. In the present work, hot filament chemical vapor deposition (HFCVD) is used to synthesize carbon nanowall (CNW) tetrapods coupled to nanocrystalline diamond in a 3D hybrid network form. The CNW/diamond phase proportion as well as the structural morphology can be easily adjusted by the CVD parameters, allowing a single‐step synthesis of CNW micro‐ and nanopillars or CNW/diamond 3D hybrid materials, in the powder form or as interconnected free‐standing specimens. Additionally, the direct incorporation of SnO2 catalyst particles during the one‐step CVD process is demonstrated. µ‐Raman and electron microscopy are used to understand the evolution of the morphological characteristics associated to the growth mechanism. The electrowettability behavior of the novel CNW/diamond hybrid material is demonstrated by electrochemical polarization studies. Such multifunctional carbon‐based hybrid 3D nanomaterials can find promising applications in advanced technologies such as energy storage. %0 journal article %@ 2046-2069 %A Mata, D.,Serdechnova, M.,Mohedano, M.,Mendis, C.L.,Lamaka, S.V.,Tedim, J.,Hack, T.,Nixon, S.,Zheludkevich, M.L. %D 2017 %J RSC Advances %N 56 %P 35357-35367 %R doi:10.1039/C7RA05593E %T Hierarchically organized Li–Al-LDH nano-flakes: a low-temperature approach to seal porous anodic oxide on aluminum alloys %U https://doi.org/10.1039/C7RA05593E 56 %X This work suggests a low-temperature sealing approach for tartaric–sulfuric acid (TSA) anodized AA2024 based on hierarchically organized Li–Al-layered double hydroxide (LDH) structures. The new proposed sealing is expected to be directly competitive to the standard hot water sealing (HWS) approaches because of its reduced treatment temperature and high protection efficiency. A hierarchical organization of in situ formed LDH nano-flakes across the depth length of the TSA pores, from the macrodown to the nano-size range, was observed with transmission electron microscopy (TEM). Electrochemical impedance spectroscopy (EIS) studies showed that the densely packed LDH arrangement at the porous oxide layer is directly related to the drastically improved barrier properties of TSA. Moreover, LDH flake-like structures worked as “smart” reservoirs for corrosion inhibiting vanadium species (VOx) that are released on demand upon the onset of corrosion. This was confirmed using a scanning vibrating electrode technique (SVET), giving relevant insights into the time-resolved release activity of VOx and the formation of the passivation layer on cathodic intermetallics, corroborated with EDX and analytical Raman spectroscopy. Passive and active corrosion protection was imparted to the anodic layer via new Li–Al-LDH structures with long-term protection exceeding that of standard HWS procedures. %0 journal article %@ 2079-6412 %A Serdechnova, M.,Mohedano, M.,Bouali, A.C.,Hoeche, D.,Kuznetsov, B.,Karpushenkov, S.,Blawert, C.,Zheludkevich, M.L. %D 2017 %J Coatings %N 11 %P 190 %R doi:10.3390/coatings7110190 %T Role of Phase Composition of PEO Coatings on AA2024 for In-Situ LDH Growth %U https://doi.org/10.3390/coatings7110190 11 %X Plasma electrolytic oxidation (PEO) is an environmentally friendly anodizing technique leading to the formation of a ceramic-like coatings under high-voltage discharges. Layered double hydroxides (LDHs) were grown directly on γ, α, and amorphous Al2O3 powders, respectively, in order to investigate the phase responsible for in-situ LDH growth on PEO coating. Furthermore, it is shown that LDH growth is limited by the high tortuosity of the PEO layer and the accessibility of Al(OH)−4,anions from the substrate covered with thin amorphous aluminum oxide, through the pores. %0 journal article %@ 0013-4651 %A Serdechnova, M.,Mohedano, M.,Kuznetsov, B.,Mendis, C.L.,Starykevich, M.,Karpushenkov, S.,Tedim, J.,Ferreira, M.G.S.,Blawert, C.,Zheludkevich, M.L. %D 2017 %J Journal of the Electrochemical Society %N 2 %P C36-C45 %R doi:10.1149/2.0301702jes %T PEO Coatings with Active Protection Based on In-Situ Formed LDH-Nanocontainers %U https://doi.org/10.1149/2.0301702jes 2 %X In the present work, for the first time Zn-Al layered double hydroxide (LDH) nanocontainers were grown in-situ on the surface and in the pores of plasma electrolytic oxidation (PEO) layer and then loaded with a corrosion inhibitor to provide active protection. The developed LDH-based conversion process ensures partial sealing of the pores and provides an effective corrosion inhibition on demand leading to increased fault-tolerance and self-healing properties. The structure, morphology and composition of the LDH-sealed PEO coatings on 2024 aluminum alloy were investigated using SEM, TEM/FIB, XRD and GDOES. Electrochemical impedance spectroscopy and scanning vibrating electrode techniques show a remarkable increase in the corrosion resistance and fault tolerance when PEO coating is sealed with a LDH-inhibitor treatment. %0 journal article %@ 1044-5803 %A Mohedano, M.,Blawert, C.,Yasakau, K.A.,Arrabal, R.,Matykina, E.,Mingo, B.,Scharnagl, N.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2017 %J Materials Characterization %N %P 85-99 %R doi:10.1016/j.matchar.2017.03.040 %T Characterization and corrosion behavior of binary Mg-Ga alloys %U https://doi.org/10.1016/j.matchar.2017.03.040 %X Four binary cast Mg-Ga alloys containing 1, 2, 3 and 4 wt% Ga were studied in terms of microstructure and degradation behavior. The alloys present two types of intermetallics: (i) the second phase Mg5Ga2, which volume increases with the amount of Ga in the alloy, and (ii) inclusions containing impurities. For the first time, the binary Mg-Ga system is analyzed paying particular attention to the effect of secondary phases (Mg5Ga2) and impurities on the localized corrosion mechanism using AFM/SKPFM. Inclusions containing impurities reveal a high Volta potential difference, enough to form an active galvanic couple. However, localized electrochemical activities decrease with time leading to uniform degradation. For short immersion times, there is no clear influence of the element Ga on the corrosion behavior, measured by electrochemical and hydrogen evolution tests. However, for longer immersion times, increasing the amount of Ga in the alloy shows a clear negative effect. Electrochemical measurements reveal that higher Ga containing alloys form faster an oxide layer which is not stable. %0 journal article %@ 0257-8972 %A Yang, J.,Lu, X.,Blawert, C.,Di, S.,Zheludkevich, M.L. %D 2017 %J Surface and Coatings Technology %N %P 359-369 %R doi:10.1016/j.surfcoat.2017.04.001 %T Microstructure and corrosion behavior of Ca/P coatings prepared on magnesium by plasma electrolytic oxidation %U https://doi.org/10.1016/j.surfcoat.2017.04.001 %X In order to enhance the corrosion resistance and biocompatibility of Mg based implants, porous MgO-CaP coatings were fabricated on commercial Mg by adding hydroxyapatite (HAp) particles in alkaline phosphate solution for plasma electrolytic oxidation (PEO) treatment. The effects of particle concentration on the coating morphology and composition were investigated under constant current PEO processing. Electrochemical impedance spectroscopy (EIS) and immersion test conducted in simulated body fluid (SBF) environment were applied to evaluate the corrosion performance of the coatings. The results showed that most HAp particles were reactively incorporated into the PEO coatings and the coating microstructure was significantly modified with increasing concentration of HA, which resulted in higher corrosion resistance in return. The consecutive growth of impedance during 72 h immersion resulted from the precipitation and deposition of CaP compound and corrosion product into the pores sealing the defects of PEO coatings. Overall, a higher concentration (20 g/L) of HAp particles addition would bring out a denser and protective PEO-HAp coating. %0 journal article %@ 1364-5072 %A Kuznetsova, A.,Domingues, P.M.,Silva, T.,Almeida, A.,Zheludkevich, M.L.,Tedim, J.,Ferreira, M.G.S.,Cunha, A. %D 2017 %J Journal of Applied Microbiology %N 5 %P 1207-1218 %R doi:10.1111/jam.13433 %T Antimicrobial activity of 2-mercaptobenzothiazole released from environmentally friendly nanostructured layered double hydroxides %U https://doi.org/10.1111/jam.13433 5 %X Aims,The objective of this work was to assess the antibacterial effect of 2‐mercaptobenzothiazole (MBT), used as model‐biocide, immobilized in a layered double hydroxide (LDH) structure, under different conditions of pH and salinity, envisaging possible applications of the system in active antifouling and anticorrosion coatings.,Methods and Results,Biological effects of MBT immobilized in LDH were assessed by monitoring bacterial bioluminescence of cell suspensions of either Allivibrio fischeri or a recombinant strain of Escherichia coli, as a proxy for bacterial activity. Salinity (1, 2 and 3% NaCl) and pH (4, 5, 6 and 7) of the suspension media were experimentally manipulated and biocide release tests were performed in parallel. The release profiles obtained by UV‐visible spectrophotometry indicated a fast release of biocide from MBT@LDH, slightly enhanced in 3% NaCl and under alkaline conditions. However, biological effects were more pronounced at 1% NaCl and at neutral pH.,Conclusions,The release and toxic effect of MBT immobilized in LDH is dependent on the concentration of solutes in the suspension medium.,Significance and Impact of the Study,The results confirm LDH as a biologically compatible material with potential to be used for biocide delivery. %0 journal article %@ 0013-4651 %A Starykevich, M.,Salak, A.N.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2017 %J Journal of the Electrochemical Society %N 6 %P D335-D341 %R doi:10.1149/2.1481706jes %T Modification of Porous Titania Templates for Uniform Metal Electrodeposition from Deep Eutectic Solvent %U https://doi.org/10.1149/2.1481706jes 6 %X Zinc electrochemical deposition in porous anodic titania from 0.5 M ZnCl2 solution in choline chloride based deep eutectic solvent is reported. Electroreduction is performed by a pulse method in titanium dioxide templates modified in three different ways. Titania nanotubes were formed in ethylene glycol based electrolyte with 0,38% (wt) ammonium fluoride and 1,79% (wt) of water. The first template has been used as-prepared, without any modification. Such a matrix shows a low fill-factor and zinc electrodeposition mainly occurs on the top of the tubes. The next template was annealed at 450°C to complete crystallization of titania. It results in electrodeposition of zinc along the entire tube surface and consequently in formation of coaxial structure. The third template was modified based on selective crystallization of the pore bottoms using higher anodization voltage (80 V) than the one used for tubes formation (40 V) in sulfuric acid electrolyte. The successful bottom-up filling of the titania nanotubes is demonstrated in this case. Investigation of the tubes filling is performed by a set of complementary techniques such as GDOES, SEM and TEM. %0 journal article %@ 0013-4651 %A Starykevich, M.,Salak, A.N.,Ivanou, D.K.,Yasakau, K.A.,Andre, P.S.,Ferreira, R.A.S.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2017 %J Journal of the Electrochemical Society %N 2 %P D88-D94 %R doi:10.1149/2.1351702jes %T Effect of the Anodic Titania Layer Thickness on Electrodeposition of Zinc on Ti/TiO2 from Deep Eutectic Solvent %U https://doi.org/10.1149/2.1351702jes 2 %X Zinc electrodeposition from a deep eutectic mixture of ZnCl2 and choline chloride/ethylene glycol on titanium covered by an anodic titania film of different thicknesses was studied. It was shown that thin titanium dioxide layers work as high resistive media and the rate of zinc deposition decreases with film thickness. Thicker titania layers (23 nm and higher) have opposite properties and the zinc reduction rate starts gradually increasing with thickness. This happens because at the higher voltage necessary to grow thicker anodic films they become more crystalline and consequently more conductive. There is also evidence that in deep eutectic solvent no dense organic layer forms on the titanium/titania electrodes. The application of an AC signal superimposed on a DC potential only marginally increases the amount of zinc deposited and FTIR measurements did not reveal the formation of any chemical bonds between the film and deep eutectic solvent. Zn deposition onto titanium/titania at −1.6 V is characterized by instantaneous three-dimensional nucleation mechanism, which is independent of the titania thickness. %0 journal article %@ 0013-4686 %A Ma, X.,Blawert, C.,Hoeche, D.,Kainer, K.U.,Zheludkevich, M.L. %D 2017 %J Electrochimica Acta %N %P 461-474 %R doi:10.1016/j.electacta.2017.08.147 %T A model describing the growth of a PEO coating on AM50 Mg alloy under constant voltage mode %U https://doi.org/10.1016/j.electacta.2017.08.147 %X Plasma electrolytic oxidation (PEO) process is employed to coat AM50 magnesium alloy in an alkaline phosphate solution applying constant voltage. Effects of treatment time on the morphology, composition and thickness of the resulting coatings are investigated by XRD and SEM respectively. Based on the analysis of the experimental results, a mathematical model is developed to simulate PEO coating growth including porosity and coating thickness. It is assumed that the current density of electrical discharges generated at the bottom of the pores remains constant and the coating growth is determined by Faraday’s law. This model describes a 2D transient finite element approach including necessary physical system parameters in mathematically coupled conditions. It demonstrates how the coating thickness is affected by current density, phase composition and porosity. The model reproduces the PEO process reasonably well and simulation results are in good agreement with experimental results, especially for predicted coating thicknesses. Although the model has a drawback in describing the oxygen release and hydroxyl ion concentration due to an empirical kinetic description, it may still be a useful tool in explaining and predicting PEO coating growth on magnesium alloy under constant DC voltage. %0 journal article %@ 0257-8972 %A Hakimizad, A.,Raeissi, K.,Golozar, M.A.,Lu, X.,Blawert, C.,Zheludkevich, M.L. %D 2017 %J Surface and Coatings Technology %N %P 208-221 %R doi:10.1016/j.surfcoat.2017.05.068 %T The effect of pulse waveforms on surface morphology, composition and corrosion behavior of Al2O3 and Al2O3/TiO2 nano-composite PEO coatings on 7075 aluminum alloy %U https://doi.org/10.1016/j.surfcoat.2017.05.068 %X Plasma electrolytic oxidation was employed to produce Al2O3 and Al2O3/TiO2 composite coatings from a silicate based electrolyte on 7075 aluminum alloy using unipolar and bipolar waveforms with cathodic duty cycle of 20 and 40%. The results showed that the surface morphology of the coatings is dependent on the applied waveform. Pancake like morphology was converted to crater like by altering waveform from unipolar to bipolar. Higher thickness, lower porosity, and thus, higher corrosion protection were achieved using the bipolar waveform at higher cathodic duty cycle of 40%. The incorporation of TiO2 nano-particles in the coatings decreased the thickness, increased the micro-cracks and widened the micro-pores on coating surface when unipolar waveform was applied. It was found that TiO2 nano-particles have been incorporated into the coatings in their original crystalline structure, i.e. rutile, which was categorized in the “inert incorporation” mode and this incorporation has not changed the matrix micro-structure, i.e. γ-alumina. In addition, the incorporated amounts of TiO2 nano-particles were constant and showed no reasonable relation with the applied waveform. The corrosion results indicated that although the composite coating produced at unipolar waveform shows the highest corrosion resistance at short periods of immersion due to repairing mechanism, it degrades at a higher rate. However, for the composite coatings produced using the bipolar waveform with the higher cathodic duty cycle of 40%, the maximum corrosion protection was achieved at long term immersion. Repairing mechanism is plugging the micro-pores in the inner compact layer which was found more effective for the coatings with lower porosity. Accordingly, it was concluded that the corrosion protection of the coatings with higher “intrinsic resistance” get more benefit from the repairing mechanism too. %0 journal article %@ 0169-4332 %A Ma, X.,Blawert, C.,Hoeche, D.,Zheludkevich, M.L.,Kainer, K.U. %D 2016 %J Applied Surface Science %N %P 304-312 %R doi:10.1016/j.apsusc.2016.01.030 %T Investigation of electrode distance impact on PEO coating formation assisted by simulation %U https://doi.org/10.1016/j.apsusc.2016.01.030 %X The influence of electrode distance between anode and cathode during plasma electrolytic oxidation (PEO) process on the coating formation was investigated by combining experiments and simulation. Firstly a model was built to simulate the effect of electrode distance on the anodic current distribution using finite element analyses. Complementary, PEO coatings were fabricated on AM50 magnesium alloy in an alkaline electrolyte with different electrode distances applying constant voltage. Phase composition, coating morphology and thickness were studied for both the front and back sides of the PEO coating depending on the electrode distance. For paralleled plate-like electrodes, based on coating uniformity, an optimum electrode distance of 60–80 mm was identified under the chosen experimental conditions. Via correlation of simulation and experimental results, the influence of electrode distance on coating formation is explored. It is demonstrated that under constant voltage mode, PEO coating formation is affected by electrode distance on both front and back sides of magnesium substrates. This effect is ascribed to the influence of electrode distance on the current distribution in the bath and to the related average current density on the surfaces. %0 journal article %@ 0257-8972 %A Lu, X.,Schieda, M.,Blawert, C.,Kainer, K.U.,Zheludkevich, M.L. %D 2016 %J Surface and Coatings Technology %N %P 287-291 %R doi:10.1016/j.surfcoat.2016.09.006 %T Formation of photocatalytic plasma electrolytic oxidation coatings on magnesium alloy by incorporation of TiO2 particles %U https://doi.org/10.1016/j.surfcoat.2016.09.006 %X Photocatalytically active plasma electrolytic oxidation coatings on AM50 Mg alloy are reported in the present work. The photocatalytic activity was achieved via introduction of anatase (TiO2 particles) to the treatment bath. The photocatalytic performance of the coating was evaluated by measuring the degradation rate of aqueous methylene blue solution and was primarily related to the anatase content on the coating surface. Lower treatment voltage and a higher amount of particles in the electrolyte can be used to incorporate more anatase into the layer and generate superior photocatalytic coatings. The tailored and functionalized surface provides new functionality for magnesium alloys. %0 journal article %@ 2046-2069 %A Kuznetsov, B.,Serdechnova, M.,Tedim, J.,Starykevich, M.,Kallip, S.,Oliveira, M.P.,Hack, T.,Nixon, S.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2016 %J RSC Advances %N 17 %P 13942-13952 %R doi:10.1039/C5RA27286F %T Sealing of tartaric sulfuric (TSA) anodized AA2024 with nanostructured LDH layers %U https://doi.org/10.1039/C5RA27286F 17 %X In this work, a functional sealing of a TSA anodic layer on AA2024 is suggested based upon the formation of inhibitor-containing Zn–Al layered double hydroxides (LDH). The LDH structures are formed in the pores of the anodic layer and on top of it as a result of hydrothermal treatment in a Zn2+-containing bath as shown by the structure, morphology and composition analysis. The resulting LDHs were loaded with a well-known corrosion inhibitor (vanadate). Electrochemical impedance spectroscopy, salt spray tests and scanning vibrating electrode techniques have shown a remarkable improvement in corrosion resistance of the LDH-modified sample in comparison with conventional hot-water sealing. The vanadate-loaded LDHs rendered a significant long-term active protection for the covered aluminum alloy substrate. %0 journal article %@ 2046-2069 %A Ivanou, D.K.,Yasakau, K.,Kallip, S.,Lisenkov, A.,Starykevich, M.,Lamaka, S.,Ferreira, M.,Zheludkevich, M. %D 2016 %J RSC Advances %N 15 %P 12553-12560 %R doi:10.1039/C5RA22639B %T Active corrosion protection coating for ZE41 magnesium alloy created by combining PEO and sol-gel techniques %U https://doi.org/10.1039/C5RA22639B 15 %X An active protective coating for ZE41 magnesium alloy was produced by sealing an anodic layer, loaded with 1,2,4-triazole, with a sol-gel film. An anodic oxide layer was formed using PEO in a silicate-fluoride alkaline solution. This thin (1.8 μm) porous PEO layer was impregnated with corrosion inhibitor 1,2,4-triazole and sealed with a silica-based sol-gel film modified with titanium oxide. For the first time it was demostrated that this relatevelly thin PEO-based composite coating reveal high barier properties and provide superior protection against corrosion attack during 1 month of continuous exposure to 3% NaCl. Scanning vibrating electrode technique showed sharp decrease (100 times) of corrosion activity in micro defects formed in 1,2,4-triazole doped composite coating, when compared to blank samples. %0 journal article %@ 0013-4686 %A Lu, X.,Blawert, C.,Kainer, K.U.,Zheludkevich, M.L. %D 2016 %J Electrochimica Acta %N %P 680-691 %R doi:10.1016/j.electacta.2016.03.042 %T Investigation of the formation mechanisms of plasma electrolytic oxidation coatings on Mg alloy AM50 using particles %U https://doi.org/10.1016/j.electacta.2016.03.042 %X The growth of plasma electrolytic oxidation (PEO) coatings can be considered a complex process that includes discharge breakdown, sintering, and deposition process. In this work, inert SiO2 and La2O3 particles were used as tracers to investigate the formation mechanisms of PEO coatings on Mg alloy AM50. The growth direction and kinetics of the coating formation are primarily controlled by the intensity and the number of discharges. High-intensity discharges enable the inward growth of the PEO coating rapidly. Low-intensity discharges allow the outward growth of the coating at a slow speed. At the initial stage of a treatment, conversion products form locally around the intermetallics and disseminate gradually. Discharges appear after reaching the breakdown potential, leading to rapid growth of the coating. The outward growth of the layer is non-uniform because the protruding conversion products are the last locations converted by the discharges. Inward growth of the layer occurs preferentially around intermetallic phases and the formation of the inner layer is related to the inward growth. %0 journal article %@ 0257-8972 %A Lu, X.,Blawert, C.,Mohedano, M.,Scharnagl, N.,Zheludkevich, M.L.,Kainer, K.U. %D 2016 %J Surface and Coatings Technology %N %P 179-185 %R doi:10.1016/j.surfcoat.2016.02.006 %T Influence of electrical parameters on particle uptake during plasma electrolytic oxidation processing of AM50 Mg alloy %U https://doi.org/10.1016/j.surfcoat.2016.02.006 %X The influence of electrical parameters on microstructure and composition of coatings by plasma electrolytic oxidation (PEO) with particle addition was investigated. PEO coatings were produced on AM50 magnesium alloy from an alkaline phosphate based electrolyte (1 g/l KOH + 20 g/l Na3PO4) with 5 g/l SiO2 particle (1–5 μm) addition. Besides the most common electrical parameters (voltage and current density), frequency and duty ratio have effect on the uptake of particles during PEO processing. Higher duty ratio and lower frequency allow to incorporate more particles into the PEO coating. The area of the melting pools, as indicated by the size and area of the open pores on the coating surface, can be considered as one important factor to determine the particle uptake during PEO processing. %0 journal article %@ 0013-4686 %A Lu, X.,Blawert, C.,Huang, Y.,Ovri, H.,Zheludkevich, M.L.,Kainer, K.U. %D 2016 %J Electrochimica Acta %N %P 20-33 %R doi:10.1016/j.electacta.2015.11.033 %T Plasma electrolytic oxidation coatings on Mg alloy with addition of SiO2 particles %U https://doi.org/10.1016/j.electacta.2015.11.033 %X The addition of particles into plasma electrolytic oxidation (PEO) electrolyte provides a possibility to produce functionalized coatings with a wider range of compositions and new phases. In this study, nano- and micro-sized SiO2 particles were in-situ incorporated into phosphate-based coatings and the effect of these particles on the microstructure, composition and properties of the coatings was investigated. It was observed that the size and the melting point of the particles have a synergistic effect on the uptake and incorporation mode. The uptake of the nanoparticles occurred mainly via discharge channels and open pores, while micro-sized particles were mainly absorbed via the coating surface. Different particle properties result in reactive and inert incorporation for the nano- and micro-sized SiO2 particles, respectively. The results show that particle additions improve the wear resistance of PEO coating, although corrosion resistance is slightly reduced. Due to superior wear performance and degradability, PEO coatings with reactively incorporated nanoparticles on Mg alloy might be suitable for bio-medical application. %0 journal article %@ 0022-4596 %A Serdechnova, M.,Salak, A.N.,Barbosa, F.S.,Vieira, D.E.L.,Tedim, J.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2016 %J Journal of Solid State Chemistry %N %P 158-165 %R doi:10.1016/j.jssc.2015.10.023 %T Interlayer intercalation and arrangement of 2-mercaptobenzothiazolate and 1,2,3-benzotriazolate anions in layered double hydroxides: In situ X-ray diffraction study %U https://doi.org/10.1016/j.jssc.2015.10.023 %X 2-mercaptobenzothiazole (MBT) and 1,2,3-benzotriazole (BTA) are very promising inhibitors for the corrosion protection of aluminum alloys. These inhibitors can be incorporated in protective coatings in the form of anions intercalated into interlayers of layered double hydroxides (LDHs). Capacity and performance of such LDH-nanocontainers depend on the arrangement of the anions in their interlayers. In this work, intercalation of MBT− and BTA− into Mg–Al–NO3 and Zn–Al–NO3 LDHs were studied in detail using X-ray diffraction (XRD) methods including in situ XRD. The nitrate-to-MBT(BTA) anion exchange is much faster than considered previously. Well-formed Mg–Al–MBT, Zn–Al–MBT, Mg–Al–BTA LDHs were obtained after a 20-min exchange reaction at pH 11.5 at room temperature. It was demonstrated that Zn–Al–BTA LDH cannot be obtained under the same conditions due to the reaction between BTA and the Zn–Al hydroxide layers. Substitution of nitrates by organic anions occurs with the participation of hydroxide anions. Although no intermediate LDH phase intercalated with the combination of NO3-NO3- and OH− appears, formation of the LDH–MBT and LDH–BTA phases results also in appearance of an LDH phase intercalated with OH− at the final stage of the anion exchange. In the LDH interlayer, MBT− and BTA− form a double layer in which these species have a tilted orientation against the layer plane (herringbone-like arrangement). Such an arrangement meets the LDH layer–interlayer electroneutrality and matches well with the observed values of the layer–interlayer distance. %0 journal article %@ 1463-9076 %A Hoeche, D.,Blawert, C.,Lamaka, S.,Scharnagl, N.,Mendis, C.,Zheludkevich, M.L. %D 2016 %J Physical Chemistry Chemical Physics %N 2 %P 1279-1291 %R doi:10.1039/C5CP05577F %T The Effect of iron re-deposition on corrosion of impurity-containing magnesium %U https://doi.org/10.1039/C5CP05577F 2 %X This article provides a contribution towards the mechanistic understanding of surface phenomena observed during corrosion of Mg-based substrates particularly in the low anodic polarization range. The concept considers recent literature explaining cathodic hydrogen evolution from noble acting areas even during global anodic polarization. Heavy metal impurities in the ppm range or intermetallics are always present even in highly pure magnesium. Their potential effect was investigated here in more detail. Experimental results contribute to understanding the role of iron impurities during dark area formation and suggest a way of linking the observed phenomena to recent literature. The shown enhanced cathodic activity of dark areas especially at the corrosion front and the superfluous hydrogen are linked to an iron re-deposition mechanism due to iron reduction. The proposed mechanism is based on results obtained from innovative characterisation techniques using magnetic fields, diffraction experiments and transmission electron microscopy, which show the formation of iron rich zones, especially at the corrosion front offering “in statu nascendi” metallic Fe films acting as active cathodes for hydrogen reduction. %0 journal article %@ 1388-2481 %A Lamaka, S.V.,Hoeche, D.,Petrauskas, R.P.,Blawert, C.,Zheludkevich, M.L. %D 2016 %J Electrochemistry Communications %N %P 5-8 %R doi:10.1016/j.elecom.2015.10.023 %T A new concept for corrosion inhibition of magnesium: Suppression of iron re-deposition %U https://doi.org/10.1016/j.elecom.2015.10.023 %X In our recent work (Höche et al. 2016) we proposed that non-faradaic dissolution of Fe impurities and/or iron containing phases with subsequent re-deposition of thin film of pure (“in statu nascendi”) iron enlarges cathodically active sites at the surface of corroding magnesium. The effect drastically accelerates corrosion of impurity containing Mg. In the present work we assume that if Fe re-deposition is prevented, the area of cathodic sites can be drastically decreased and hence corrosion of Mg can be suppressed. In this proof of concept work we use strong Fe3 + complexing agents in order to remove dissolved iron cations from corrosion sites and prevent iron re-deposition. All used iron complexing agents efficiently lowered the corrosion rate of Mg. Direct correlation of complex stability with its inhibiting efficiency was established. It was shown that cyanide, salicylate, oxalate, methylsalicylate and thiocyanate efficiently reduce hydrogen evolution and suppress critical dark area formation. %0 journal article %@ 0257-8972 %A Lu, X.,Mohedano, M.,Blawert, C.,Matykina, E.,Arrabal, R.,Kainer, K.U.,Zheludkevich, M.L. %D 2016 %J Surface and Coatings Technology %N %P 1165-1182 %R doi:10.1016/j.surfcoat.2016.08.055 %T Plasma electrolytic oxidation coatings with particle additions – A review %U https://doi.org/10.1016/j.surfcoat.2016.08.055 %X Plasma electrolytic oxidation (PEO) processing for light metals is known for decades and has been established as a well-known industrial surface treatment offering a reasonable wear and corrosion protection. However, long-term protection is compromised by the intrinsic porosity and limited range of composition in the PEO layer. A novel approach is to introduce particles to the electrolyte, aiming at their in-situ incorporation into PEO coatings during growth. The idea is that with the help of particles the defects can be sealed, and the composition range and the functionalities of produced coatings can be enhanced. So far, multifunctional coatings with anticorrosion, self-lubrication, anti-wear, bioactive and photocatalytic properties were produced with the aid of particle addition.,The properties of particle itself, together with electrical and electrolyte parameters during PEO processing determine the way and efficiency of particle uptake and incorporation into the coatings. Normally incorporation of the particles into the coating can range from fully inert to fully reactive. This paper reviews recent progress on particle-containing PEO coatings formed on Mg, Al and Ti alloy substrates. The main focus is given to the uptake mechanism of particle into PEO layers and the introduced microstructural and functional changes. %0 journal article %@ 1559-3959 %A Bardushkin, V.V.,Shilyaeva, Y.I.,Gavrilov, S.A.,Silibin, M.V.,Yakovlev, V.B.,Zheludkevich, M.L.,Popenko, N.I. %D 2016 %J Journal of Mechanics of Materials and Structures %N 5 %P 583-594 %R doi:10.2140/jomms.2016.11.583 %T Predictive modeling of mechanical properties of metal filled anodic aluminum oxide %U https://doi.org/10.2140/jomms.2016.11.583 5 %X Filling dielectric porous matrices, particularly anodic aluminum oxide, with metal confers a promising solution for nanocomposite creation. In this regard, the problem of estimating and predicting the physical and mechanical properties of such materials is of prime importance. The present work focuses on the numerical modeling of the effective and ultimate stress-strain (under compression) characteristics of nanocomposites based on anodic aluminum oxide with unidirectional filamentary pores filled with different metals (In, Sn, and Zn). The dependences of the tensor components of the effective elastic moduli, coefficients of elastic anisotropy (in different directions), and compression strength (along the nanowires) on the structure parameters and the concentration of nanowires are investigated. %0 journal article %@ 0142-2421 %A Mohedano, M.,Matykina, E.,Arrabal, R.,Mingo, B.,Zheludkevich, M. %D 2016 %J Surface and Interface Analysis :SIA %N 8 %P 953-959 %R doi:10.1002/sia.5815 %T PEO of rheocast A356 Al alloy: Energy efficiency and Corrosion properties %U https://doi.org/10.1002/sia.5815 8 %X PEO coatings were developed under voltage-controlled mode on a rheocast A356 aluminum alloy without and with pretreatment by conventional anodizing in sulphuric acid. Microstructure and composition of uncoated and coated materials were studied using SEM, EDS and XRD. The anodic precursor oxide layer preserves the microstructure of the alloy because of the presence of secondary phases having a different behavior relative to the matrix during conventional anodizing. After PEO treatment, the coatings consisted of a mixture of α-Al2O3, γ-Al2O3, SiO2 and mullite (3Al2O3·2SiO2). The effect of pre-anodizing on energy efficiency was investigated revealing considerable energy savings with the precursor porous films, because of the faster establishment of the so-called ‘soft sparking’ regime that promotes faster coating growth rate. The electrochemical corrosion properties were evaluated for uncoated and coated materials using electrochemical techniques (potentiodynamic curves and electrochemical impedance spectroscopy). PEO coated materials showed remarkably reduced susceptibility to corrosion. %0 journal article %@ 0169-4332 %A Yasakau, K.A.,Giner, I.,Vree, C.,Ozcan, O.,Grothe, R.,Oliveira, A.,Grundmeier, G.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2016 %J Applied Surface Science %N %P 144-156 %R doi:10.1016/j.apsusc.2016.07.093 %T Influence of stripping and cooling atmospheres on surface properties and corrosion of zinc galvanizing coatings %U https://doi.org/10.1016/j.apsusc.2016.07.093 %X In this work the influence of stripping/cooling atmospheres used after withdrawal of steel sheet from Zn or Zn-alloy melt on surface properties of Zn (Z) and Zn-Al-Mg (ZM) hot-dip galvanizing coatings has been studied. The aim was to understand how the atmosphere (composed by nitrogen (N2) or air) affects adhesion strength to model adhesive and corrosive behaviour of the galvanized substrates. It was shown that the surface chemical composition and Volta potential of the galvanizing coatings prepared under the air or nitrogen atmosphere are strongly influenced by the atmosphere. The surface chemistry Z and ZM surfaces prepared under N2 contained a higher content of metal atoms and a richer hydroxide density than the specimens prepared under air atmosphere as assessed by X-ray photoelectron spectroscopy (XPS). The induced differences on the microstructure of the galvanized coatings played a key role on the local corrosion induced defects as observed by means of in situ Atomic force microscopy (AFM). Peel force tests performed on the substrates coated by model adhesive films indicate a higher adhesive strength to the surfaces prepared under nitrogen atmosphere. The obtained results have been discussed in terms of the microstructure and surface chemical composition of the galvanizing coatings. %0 journal article %@ 1432-881X %A Galvao, T.L.P.,Kuznetsova, A.,Gomes, J.R.B.,Zheludkevich, M.L.,Tedim, J.,Ferreira, M.G.S. %D 2016 %J Theoretical Chemistry Accounts %N 3 %P 78 %R doi:10.1007/s00214-016-1839-3 %T A computational UV–Vis spectroscopic study of the chemical speciation of 2-mercaptobenzothiazole corrosion inhibitor in aqueous solution %U https://doi.org/10.1007/s00214-016-1839-3 3 %X In order to understand the chemical speciation of 2-mercaptobenzothiazole (MBT) corrosion inhibitor as a function of pH, the experimental electronic absorption spectra was compared with those calculated at the EOM-CCSD, TD-M06-2X and TD-B3LYP levels of theory for several different species that may result from MBT reactions in aqueous solution. The computational spectroscopic analysis was supported by the energetics of tautomerization, deprotonation, non-covalent association and ion-pair formation reactions calculated at the M06-2X/6-31++G(d,p) level of theory. The thioketonic and deprotonated anionic forms of MBT were found to be the main species depending on the pH, while the formation of the ion-pair was also supported under basic conditions, especially when put in perspective of the release profiles of the inhibitor from nanocontainers published in the literature. The calculated energetic and electronic results were used to unveil the tautomeric, acid–base and ion-pair formation equilibrium, relevant to guide the application of MBT as a corrosion inhibitor, and establishing a foundation for future molecular modeling studies concerning the adsorption of MBT onto metal and metal alloys under different pHs. %0 journal article %@ 0933-5137 %A Rico-Oller, B.,Mertens, T.,Kolb, M.,Wehr, J.,Zheludkevich, M.L. %D 2016 %J Materials Science and Engineering Technology - Materialwissenschaft und Werkstofftechnik %N 5-6 %P 400-408 %R doi:10.1002/mawe.201600515 %T Environmentally friendly anodising process for structural bonding of titanium - Umweltfreundliches Eloxierverfahren fuer strukturelles Verkleben von Titan %U https://doi.org/10.1002/mawe.201600515 5-6 %X This paper evaluates the applicability of two wet-chemical treatments for structural bonding of titanium alloy Ti6Al4V. The anodising processes, NaTESi and N4-Process, are based on electrolytes containing sodium hydroxide and complexing agents, but while NaTESi process contains ethylenediaminetetraacetic acid, a particularly hazardous chemical, N4-Process is a REACh compliant electrolyte. Scanning electron microscopy and transmission electron microscopy were employed to evaluate the oxide layer formed after the anodising processes. The long-term durability and the resultant adhesion properties on titanium were assessed by means of floating-roller-peel test. Both investigated anodising processes lead to oxide layers revealing a highly porous nanostructure (thickness between 150–600 nm) according to scanning electron microscopy and transmission electron microscopy analyses. The mechanical tests lead to negligible differences between processes, performing higher peel resistance when compared to only alkaline etched samples, especially after 1000 hours ageing at 50 °C and 95 % relative humidity. The results indicate that N4-Process is a promising treatment to enhance the long-term durability of bonded titanium joints, especially under hot and wet conditions.,In diesem Artikel wird die Anwendbarkeit von nasschemischen Vorbehandlungen für das strukturelle Kleben von Ti6Al4V Titanlegierungen untersucht. Die untersuchten Anodisierprozesse, NaTESi und N4, basieren auf Elektrolyten mit Natriumhydroxid und Komplexbildner. Während beim NaTESi-Prozess Ethylendiamintetraessigsäure als Komplexbildner eingesetzt wird, kommt beim N4-Prozess ein REACh-konformer Komplexbildner zum Einsatz. Die resultierenden Oberflächen werden mittels Rasterelektronen- und Transmissionselektronenmikroskopie charakterisiert. Neben der Oberflächentopografie werden auch die Haftungseigenschaften der resultierenden Oberfläche geprüft. Hierzu wird der Rollenschältest sowohl im trockenen Zustand als auch nach der Auslagerung im feucht-warmen Klima durchgeführt. Die Charakterisierung der Oberflächentopographie zeigt, dass beide Prozesse zu einer nanostrukturierten und kristallinen Oxidschicht mit einer Dicke zwischen 150 nm und 600 nm führen. Die Ergebnisse der Rollenschältests verdeutlichen, dass beide Prozesse zu vergleichbaren Schälfestigkeiten führen. Im Vergleich zu einer nur alkalisch gebeizten Probe, konnten jedoch deutlich höhere Festigkeiten erzielt werden. Vor allem nach der Alterung der Proben für 1000 h bei 50 °C und 95 % rH, lassen sich deutliche Unterschiede erkennen. Während die nur gebeizten Proben einen deutlichen Abfall in der Schälfestigkeit zeigen, führen die Verfahren NaTESi und N4-Prozess zu einer guten Langzeitstabilität. %0 journal article %@ 0013-4651 %A Lisenkov, A.D.,Poznyak, S.K.,Zheludkevich, M.L,Ferreira, M.G.S. %D 2016 %J Journal of the Electrochemical Society %N 7 %P C364-C368 %R doi:10.1149/2.0881607jes %T Aluminum Anodization in Deionized Water as Electrolyte %U https://doi.org/10.1149/2.0881607jes 7 %X Thin oxide films were prepared electrochemically on the aluminum surface using the high-voltage discharge and potentiostatic methods in deionized water as an electrolyte. The growth of continuous films occurred only at potentials lower than the breakdown potential. The films obtained by the discharge method are more uniform and can grow to a higher thickness in comparison to those formed by the potentiostatic mode, as demonstrated by electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM), and scanning Kelvin probe force microscopy (SKPFM). The data herein obtained can be used as a reference to understand better the properties of the films produced in conventional electrolytes where apart from water other species are present. %0 journal article %@ 0013-4686 %A Tedim, J.,Bastos, A.C.,Kallip, S.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2016 %J Electrochimica Acta %N %P 215-224 %R doi:10.1016/j.electacta.2016.05.134 %T Corrosion protection of AA2024-T3 by LDH conversion films. Analysis of SVET results %U https://doi.org/10.1016/j.electacta.2016.05.134 %X In this work the protective effect of layered double hydroxide (LDH) films directly grown on the surface of 2024-T3 aluminium alloy is investigated using electrochemical impedance spectroscopy (EIS) and the scanning vibrating electrode technique (SVET). The SVET results focused on the localised nature of the corrosion process and are in agreement with the global response measured by EIS. Furthermore, the evolution of active corrosion protection rendered by LDH films is surveyed at microscale for the first time for long immersion periods in NaCl solution and in the presence of induced defects. The quantitative information provided by SVET is discussed and a parameter to describe the degree of corrosion localisation is introduced based on LDH systems. %0 journal article %@ 1385-8947 %A Maia, F.,Yasakau, K.A.,Carneiro, J.,Kallip, S.,Tedim, J.,Henriques, T.,Cabral, A.,Venancio, J.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2016 %J Chemical Engineering Journal %N %P 1108-1117 %R doi:10.1016/j.cej.2015.07.087 %T Corrosion protection of AA2024 by sol–gel coatings modified with MBT-loaded polyurea microcapsules %U https://doi.org/10.1016/j.cej.2015.07.087 %X In this work we report the synthesis of polyurea microcapsules loaded with corrosion inhibitor 2-mercaptobenzothiazole (MBT) for corrosion protection of 2024 aluminum alloy. The microcapsules were prepared by interfacial polycondensation. The resulting capsules exhibit spherical shape, with diameter ranging between 100 nm and 2 μm. The loading content of MBT was found to be 5 wt% and release studies showed that MBT is preferentially released under acidic and alkaline conditions and follows a Fickian diffusion model. This pH dependency seems suitable for protection of metallic alloys where corrosion processes are accompanied by local pH changes. Furthermore, the microcapsules were added to a hybrid sol–gel coating and its performance assessed by electrochemical and accelerated standard tests. The results obtained indicate that capsules loaded with MBT do not affect negatively the barrier properties of sol–gel coatings, and contribute for the enhancement of adhesion of coatings to the metallic substrate. More relevant, these additives impart active corrosion protection suppressing corrosion activity at defect sites, which opens prospects for application of polyurea microcapsules as additives for high-performance coatings. %0 journal article %@ 0257-8972 %A Chen, Y.,Yang, Y.,Zhang, T.,Zhang, W.,Wang, F.,Lu. X.,Blawert, C.,Zheludkevich, M.L. %D 2016 %J Surface and Coatings Technology %N %P 825-836 %R doi:10.1016/j.surfcoat.2016.09.031 %T Interaction effect between different constituents in silicate-containing electrolyte on PEO coatings on Mg alloy %U https://doi.org/10.1016/j.surfcoat.2016.09.031 %X The influence of different constituents in silicate containing alkaline electrolytes on PEO-coated AZ91D magnesium alloy has been systematically studied using response surface methodology (RSM) coupled with electrochemical measurements and microstructure characterization methods. The results indicate that the most dominant factor that determines the coating performance is the interaction between Na2SiO3 and NaOH, where better corrosion resistance could be achieved when their concentrations are tuned in different directions. Infrared spectrum analysis of the electrolytes innovatively indicates that the degree of polymerization of silicate ions (from one to two- and three-dimensional), varied by the concentration of Na2SiO3 and NaOH, influences the kinetic mechanism of coating formation and thermal-driven gel-forming process under sparking. When silicates species exist as a relatively higher polymerized state, which indicates lower mobility of silicates in the electrolyte and better affinity for trapping Al3 + to form gel-like networks, the resulting coating is inhomogeneous and susceptible to corrosive ions; otherwise, the coating is more homogeneous and exhibits improved corrosion resistance. The work herein aims to provide guidelines for designing PEO electrolyte via correlating the intrinsic nature of the electrolyte with coating properties. %0 journal article %@ 0013-4686 %A Yasakau, K.A.,Kallip, S.,Lisenkov, A.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2016 %J Electrochimica Acta %N %P 126-141 %R doi:10.1016/j.electacta.2016.06.045 %T Initial stages of localized corrosion at cut-edges of adhesively bonded Zn and Zn-Al-Mg galvanized steel %U https://doi.org/10.1016/j.electacta.2016.06.045 %X The mechanisms of the initial stages of localized corrosion at cut edges were investigated for adhesively bonded Zn (Z) and Zn-Al-Mg (ZM) galvanized steel. The results provided strong evidence for the localized nature of corrosion of galvanized coatings at the cut edges and at the adhesive/zinc interface. In both cases a defined localized corrosion attack on zinc in Z sample was observed. On the contrary, in the case of the ZM specimen both zinc solid solution and eutectics exhibited local corrosion. The local attack at the adhesive/Z(ZM) interface was correlated with an anodic undermining process. It develops near the cut-edge surface and at the buried deep adhesive-zinc interface and results in adhesive disbonding in the buried interface. The electrochemical studies revealed that the corrosion kinetics at the metal cut-edges decreases during immersion, which could be due to formation of corrosion products on both steel and zinc surfaces. %0 journal article %@ 2452-3216 %A Alexopoulos, N.D.,Proiou, A.,Dietzel, W.,Blawert, C.,Heitmann, V.,Zheludkevich, M.,Kourkoulis, S.K. %D 2016 %J Procedia Structural Integrity %N %P 597-603 %R doi:10.1016/j.prostr.2016.06.077 %T Mechanical properties degradation of (Al-Cu-Li) 2198 alloy due to corrosion exposure %U https://doi.org/10.1016/j.prostr.2016.06.077 %X The present work investigates the corrosion resistance of the innovative Al-Cu-Li (2198) aluminum alloy; a comparison against Al-Cu (2024) alloy is attempted. Tensile specimens were pre-corroded for different exposure times to exfoliation corrosion solution and immediately afterwards they were tested in tension. For small exposure times (< 12 h) small pits could be found on the corroded surfaces; pitting was also noticed at the small side surfaces (thickness) of the tensile specimens. Corrosion exposure seems not to essentially decrease the yield stress of AA2198 even for high exposure times, while this was not the case for AA2024. After heavy corrosion exposure (>12 h), AA2024 lost almost 30% of its initial ultimate tensile strength, while for AA2198 the respective value was only 11%. Al-Cu-Li alloy shows superior corrosion resistance in terms of maintaining higher percentages of tensile ductility; AA2198 exhibited higher remaining elongation at fracture values due to corrosion degradation for all investigated exposure times. %0 journal article %@ 0010-938X %A Zhang, Y.,Blawert, C.,Tang, S.,Hu, J.,Mohedano, M.,Zheludkevich, M.L.,Kainer, K.U. %D 2016 %J Corrosion Science %N %P 483-494 %R doi:10.1016/j.corsci.2016.08.013 %T Influence of surface pre-treatment on the deposition and corrosion properties of hydrophobic coatings on a magnesium alloy %U https://doi.org/10.1016/j.corsci.2016.08.013 %X Calcium stearate based hydrophobic coatings were deposited on pre-treated Mg alloy substrates. The influence of four different pre-treatments including plasma electrolytic oxidation (as prepared and etched), anodizing and hydrothermal treatment was studied. The results indicate that the pre-treatments have strong influences on the morphology, thickness, and wettability of the coatings, without affecting their phase composition. The coating system based on the etched plasma electrolytic oxidation pre-treatment shows the best corrosion resistance in a simulated body fluid. The superior protection effect is mainly related to the differences in the morphologies and thickness of the pre-treatment layers. %0 journal article %@ 0257-8972 %A Lu, X.,Sah, S.P.,Scharnagl, N.,Stoermer, M.,Starykevich, M.,Mohedano, M.,Blawert, C.,Zheludkevich, M.L.,Kainer, K.U. %D 2015 %J Surface and Coatings Technology %N %P 155-169 %R doi:10.1016/j.surfcoat.2014.11.027 %T Degradation behavior of PEO coating on AM50 magnesium alloy produced from electrolytes with clay particle addition %U https://doi.org/10.1016/j.surfcoat.2014.11.027 %X Amorphous plasma electrolytic oxidation (PEO) coating with sealed discharge channels can be formed in alkaline phosphate electrolyte containing montmorillonite clay particles. The effect of various concentrations of phosphate and hydroxide ions in the clay-containing electrolyte on the microstructure of the coatings was studied in the present work and correlated with the corrosion behavior. The clay particles were reactively incorporated into the coating. Single amorphous phase appears in PEO coatings produced from electrolytes containing higher concentration of phosphate. These amorphous coatings are degrading within a relatively short period in 0.5 wt% NaCl solution. Electrolytes containing higher concentration of KOH tend to produce mixed PEO coatings composed of crystalline and amorphous phases. These layers demonstrate higher corrosion resistance and degradation stability. Thus, the degradation rate of PEO coatings is governed mostly by the stability of their phase composition, which might be controlled by varying electrolyte composition. %0 journal article %@ 0257-8972 %A Muhaffel, F.,Mert, F.,Cimenoglu, H.,Hoeche, D.,Zheludkevich, M.L.,Blawert, C. %D 2015 %J Surface and Coatings Technology %N %P 200-211 %R doi:10.1016/j.surfcoat.2014.12.057 %T Characterisation and corrosion behaviour of plasma electrolytic oxidation coatings on high pressure die cast Mg–5Al–0.4Mn–xCe (x = 0, 0.5, 1) alloys %U https://doi.org/10.1016/j.surfcoat.2014.12.057 %X In the present study, the influence of minor cerium (Ce) additions (up to 1 wt.%) to AM50 magnesium alloy on the plasma electrolytic oxidation (PEO) process and the corrosion performance of the PEO coatings were studied. Therefore, a silicate-based PEO coating was deposited on AM50 containing 0, 0.5 and 1 wt.% Ce under the same processing conditions. The resulting surface morphology, cross-sectional microstructure, phase and chemical compositions of the coatings were determined using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analyses (XRD). The corrosion behaviour of the coatings was evaluated by salt spray and electrochemical corrosion tests.,The results show that the growth rate of the coating is reduced, but the thickness is becoming more uniform if cerium is added to AM50 alloy. However, the phase composition and coating morphology are hardly influenced, but the corrosion properties reveal large differences suggesting that the porous PEO coatings have to be considered as a system of coating and substrate. A more uniform corroding substrate such as the cerium alloyed AM50 provides much better protection in combination with a PEO coating than the pure AM50. Flaking-off of large coating areas was observed due to the volume increase caused by corrosion products forming in the interface. Such a severe localised corrosion in the interface causing delamination of the coating can be suppressed by cerium addition. %0 journal article %@ 0257-8972 %A Mohedano, M.,Blawert, C.,Zheludkevich, M.L. %D 2015 %J Surface and Coatings Technology %N %P 145-154 %R doi:10.1016/j.surfcoat.2015.01.003 %T Cerium-based sealing of PEO coated AM50 magnesium alloy %U https://doi.org/10.1016/j.surfcoat.2015.01.003 %X Environmentally friendly Ce-based sealing post-treatments were developed for PEO coatings on AM50 magnesium alloy. The influence of the Ce(NO3)3 concentration in the Ce bath and the time of the sealing process were evaluated in terms of morphological and structural properties using SEM, EDS and XRD. Ce content in the layer increased with both the amount of salt in the solution and the time of the sealing post-treatment process due to a higher Ce product accumulation into the pores and cracks of the coatings. Sealed PEO coatings revealed an improvement in the corrosion protection properties as measured by electrochemical impedance spectroscopy. Differences in the corrosion resistance values for the sealed coatings indicate a strong relation between the parameters of the sealing process and its effectiveness, showing higher resistance for the sealed PEO coating developed after 3 h of immersion in 10 g/l Ce(NO3)3 sealing bath. %0 journal article %@ 1947-2935 %A Kalanda, N.A.,Kovalev, L.V.,Waerenborgh, J.C.,Soares, M.R.,Zheludkevich, M.L.,Yarmolich, M.V.,Sobolev, N.A. %D 2015 %J Science of Advanced Materials %N 3 %P 446-454 %R doi:10.1166/sam.2015.2134 %T Interplay of Superstructural Ordering and Magnetic Properties of the Sr2FeMoO6–δ Double Perovskite %U https://doi.org/10.1166/sam.2015.2134 3 %X Strontium ferromolybdate (Sr2FeMoO6–δ , SFMO) is a material exhibiting promising magnetoresistive properties. We have synthesized SFMO samples out of simple oxides (SrCO3, Fe2O3, and MoO3 or partially reduced SrFeO3–x (SFO) and SrMoO4–y (SMO) precursors. The samples have been experimentally investigated using X-ray diffraction, temperature-dependent magnetization, Mössbauer effect and ferromagnetic resonance measurements. Samples of the first type contain a high density of defects, especially [FeMo], [MoFe] antisites, and do not exhibit any superstructural ordering of the iron and molybdenum ions (P = 0%). These samples comprise iron cations in a mixed valence state, Fe2+ / 3+, and are characterized by a higher magnetic inhomogeneity than those synthesized out of precursors. The use of the latter increases the sample density and brings about a growth acceleration, synthesis temperature reduction, as well as the appearance of a superstructural ordering of the Fe3+ and Mo5+ cations with P = 64%. The samples exhibit magnetic anisotropy and consist of nanosize grains. Zero-field-cooling measurements of the temperature dependences of the magnetization reveal a sudden leap of the magnetization at low temperatures (below 23 K) that witnesses the existence of magnetic regions with a low coercivity, in which a superparamagnetic state exists. The obtained results are important for the optimization of the synthesis technology of SFMO for device applications. %0 journal article %@ 2046-2069 %A Carneiro, J.,Caetano, A.F.,Kuznetsova, A.,Maia, F.,Salak, A.N.,Tedim, J.,Scharnagl, N.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2015 %J RSC Advances %N 50 %P 39916-39929 %R doi:10.1039/C5RA03741G %T Polyelectrolyte-modified layered double hydroxide nanocontainers as vehicles for combined inhibitors %U https://doi.org/10.1039/C5RA03741G 50 %X In this work, nanocontainers based on layered double hydroxide (LDH) loaded with two different corrosion inhibitors, namely 2-mercaptobenzothiazole (MBT) and cerium(III) nitrate, were prepared. MBT was intercalated into LDH galleries in anionic form by anion-exchange, while Ce3+ was fixed between polyelectrolyte layers on the surface of LDH-MBT nanoplatelets by the Layer-by-Layer (LbL) method. Both inhibitors were found in the modified LDHs (LDH-Mod) by X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. The release studies performed by UV-vis spectrophotometry indicated that the main triggering conditions for release of MBT from LDHs changed when LDH nanoplatelets were covered with polyelectrolytes. Furthermore, electrochemical impedance spectroscopy and DC polarization were used to investigate the effect in combining MBT− and Ce3+ within the same nanocontainer, for the corrosion protection of 2024-T3 aluminium alloy directly in solution as well as in a hybrid sol–gel coating. The obtained results open prospects for application of these systems as additives in multifunctional smart coatings. %0 journal article %@ 0261-3069 %A Mohedano, M.,Blawert, C.,Zheludkevich, M.L. %D 2015 %J Materials and Design %N %P 735-744 %R doi:10.1016/j.matdes.2015.07.132 %T Silicate-based Plasma Electrolytic Oxidation (PEO) coatings with incorporated CeO2 particles on AM50 magnesium alloy %U https://doi.org/10.1016/j.matdes.2015.07.132 %X Plasma Electrolytic Oxidation (PEO) coatings on AM50 were developed in electrolytes containing CeO2 particles. The effect of particle concentration in the electrolyte on the final microstructure of the coatings was studied and correlated with the corrosion behavior. CeO2 particles were incorporated into the coatings and located preferentially in pores and cracks. The process involves both uptake and reactive incorporation of CeO2 under local melting caused by microdischarges.,The coating with the lower concentration of particles has the best corrosion properties as measured with EIS. Higher concentration of particles increased the defect density in the coating which has a negative effect on the corrosion resistance. %0 journal article %@ 1862-6300 %A Salak, A.N.,Ignatenko, O.V.,Zhaludkevich, A.L.,Lisenkov, A.D.,Starykevich, M.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2015 %J Physica Status Solidi A %N 4 %P 791-795 %R doi:10.1002/pssa.201431820 %T High-pressure zinc oxysulphide phases in the ZnO–ZnS system %U https://doi.org/10.1002/pssa.201431820 4 %X Wurtzite–zincblende mixture, ZnO–ZnS (1:1 wt.%), was thermally treated at 5 GPa in order to explore a possible mutual solubility of the end members and formation of zinc oxysulphide phases under high pressure. The data on phase content, crystal structure, and microstructure from the X-ray diffraction and the scanning electron microscopy studies of the obtained compacts (ceramics) were compared and analyzed. It was found that as temperature is increased, the following processes occur in the ZnO–ZnS mixture under pressure: release of the mechanical stresses (between about 300 and 700 °C), recrystallization of the initial wurtzite and zincblende phases (700–900 °C), reaction between the end members (above ∼900 °C) that results in formation of mixed oxysulphides based on ZnO and ZnS, respectively, with the mutual solubility rate of about 8 mol.%. %0 journal article %@ 0013-4686 %A Starykevich, M.,Salak, A.N.,Ivanou, D.K.,Lisenkov, A.D.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2015 %J Electrochimica Acta %N %P 284-291 %R doi:10.1016/j.electacta.2015.04.150 %T Electrochemical deposition of zinc from deep eutectic solvent on barrier alumina layers %U https://doi.org/10.1016/j.electacta.2015.04.150 %X The direct use of high-ordered porous templates of anodic aluminium oxide for formation of nanostructures via electrochemical deposition is difficult because the presence of the of barrier alumina layer in the bottom of pores. In this paper, zinc electrodeposition from a solution of ZnCl2 in a choline chloride/ethylene glycol eutectic mixture on dense alumina layers of different thicknesses was studied. In a potentiostatic regime, the deposition on a barrier layer was found to be hardly possible even when the layer is a native alumina film (about 2 nm thick). Choline and ethylene glycol form an adsorbed stable layer at the alumina/electrolyte interface and thereby block the access of zinc chloride anions to the electrode.,It has been shown that zinc can be directly deposited on a barrier layer by means of application of a combined potential mode in which an AC component of 50 mV superimposed on the DC potential of −1.6 V. Increasing the temperature of the eutectic solution allows zinc electrodeposition in a potentiostatic regime already at 50 °C. By application of any of these conditions, zinc can be deposited on a barrier alumina layer up to about 60 nm thick. The range of frequencies of the AC component and the temperature range where the deposition is optimal were considered. The mechanism of unblocking of the electrode by the alternating potential and by the temperature rise has been suggested. %0 journal article %@ 0010-938X %A Oliveira, A.B.,Bastos, A.C.,Fernandes, C.M.,Pinho, C.M.S.,Senos, A.M.R.,Soares, E.,Sacramento, J.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2015 %J Corrosion Science %N %P 322-331 %R doi:10.1016/j.corsci.2015.08.006 %T Corrosion behaviour of WC-10% AISI 304 cemented carbides %U https://doi.org/10.1016/j.corsci.2015.08.006 %X The corrosion behavior of tungsten carbide hard metal composites with AISI 304L stainless steel as binder matrix and a WC–Co composite with similar grain size and binder content was investigated using electrochemical techniques (open circuit potential monitoring, current-potential curves, electrochemical impedance spectroscopy, scanning vibrating electrode technique) and scanning electron microscopy. %0 journal article %@ 0010-938X %A Lu, X.,Blawert, C.,Zheludkevich, M.L.,Kainer, K.U. %D 2015 %J Corrosion Science %N %P 201-207 %R doi:10.1016/j.corsci.2015.09.016 %T Insights into plasma electrolytic oxidation treatment with particle addition %U https://doi.org/10.1016/j.corsci.2015.09.016 %X Plasma electrolytic oxidation (PEO) processing has received considerable attention for improving the corrosion or wear resistance of magnesium and its alloys. However, it cannot provide high-barrier long-term protection due to its high porosity. A novel approach is to introduce reactive particles to PEO coatings, aiming to seal the porosity and to provide wider range of coating compositions. Experiments with nano- and micro-sized SiO2 particles and different concentrations of KOH in the electrolyte provide new insights into possible up-take and incorporation mechanisms of particles during PEO processing. %0 journal article %@ 1385-8947 %A Maia, F.,Silva, A.P.,Fernandes, S.,Cunha, A.,Almeida, A.,Tedim, J.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2015 %J Chemical Engineering Journal %N %P 150-157 %R doi:10.1016/j.cej.2015.01.076 %T Incorporation of biocides in nanocapsules for protective coatings used in maritime applications %U https://doi.org/10.1016/j.cej.2015.01.076 %X This work reports the synthesis and characterization of silica nanocapsules with biologically-active compounds 2-mercaptobenzothiazole and 4,5-dichloro-2-octyl-4-isothiazolin-3-one. The resulting particles were characterized by scanning electron microscopy, thermogravimetry and adsorption–desorption isotherms of N2. The antibacterial activity was assessed for both nanocapsules dispersed in solution as well as incorporated in coating systems, using a recombinant bioluminescent Escherichia coli expressing the luxCDABE genes from the marine bioluminescent bacterium Aliivibrio fischeri. The decrease in light emission of the bacterial model, indicative as decrease of metabolic activity, was directly correlated with the level of biocide detected in solution by UV–Visible spectrophotometry. The results show that the developed nanomaterials show great potential for application in antifouling coatings. %0 journal article %@ 0003-2700 %A Silva, E.L.,Gouvea, C.P.,Quevedo, M.C.,Neto, M.A.,Archanjo, B.S.,Fernandes, A.J.S.,Achete, C.A.,Silva, R.F.,Zheludkevich, M.L.,Oliveira, F.J. %D 2015 %J Analytical Chemistry %N 13 %P 6487-6492 %R doi:10.1021/acs.analchem.5b00756 %T All-Diamond Microelectrodes as Solid State Probes for Localized Electrochemical Sensing %U https://doi.org/10.1021/acs.analchem.5b00756 13 %X The fabrication of an all-diamond microprobe is demonstrated for the first time. This ME (microelectrode) assembly consists of an inner boron doped diamond (BDD) layer and an outer undoped diamond layer. Both layers were grown on a sharp tungsten tip by chemical vapor deposition (CVD) in a stepwise manner within a single deposition run. BDD is a material with proven potential as an electrochemical sensor. Undoped CVD diamond is an insulating material with superior chemical stability in comparison to conventional insulators. Focused ion beam (FIB) cutting of the apex of the ME was used to expose an electroactive BDD disk. By cyclic voltammetry, the redox reaction of ferrocenemethanol was shown to take place at the BDD microdisk surface. In order to ensure that the outer layer was nonelectrically conductive, a diffusion barrier for boron atoms was established seeking the formation of boron–hydrogen complexes at the interface between the doped and the undoped diamond layers. The applicability of the microelectrodes in localized corrosion was demonstrated by scanning amperometric measurements of oxygen distribution above an Al–Cu–CFRP (Carbon Fiber Reinforced Polymer) galvanic corrosion cell. %0 journal article %@ 1944-8244 %A Kovalev, L.V.,Yarmolich, M.V.,Petrova, M.L.,Ustarroz, J.,Terryn, H.A.,Kalanda, N.A.,Zheludkevich, M.L. %D 2014 %J ACS Applied Materials and Interfaces %N 21 %P 19201-19206 %R doi:10.1021/am5052125 %T Double Perovskite Sr2FeMoO6 Films Prepared by Electrophoretic Deposition %U https://doi.org/10.1021/am5052125 21 %X The present work reports on the new approach to create metal-supported Sr2FeMoO6 (SFMO)-based electrodes that have high potential to be applied in solid oxide fuel cells. The SFMO films were formed on stainless steel substrates by electrophoretic deposition (EPD) method. Ethyl alcohol with phosphate ester as a dispersant and isopropyl alcohol with I2-acetone mixture as a charge additive were considered as an effective medium for EPD of SFMO particles. The synthesis of SFMO powder as well as suspension preparation and deposition kinetics were systematically studied. The effect of applied voltage on the thickness and morphology of SFMO films was established. The microstructure of the deposits was examined by electron microscopy. The thickness, morphology and porosity of the SFMO layers can be fine-tuned by varying solvent, charging additives, deposition time, and applied voltage. According to X-ray photoelectron spectroscopy analysis, it was found that Fe3+–Mo5+ and Fe2+–Mo6+ pairs coexist, whereas the valent balance shifts toward an Fe2+–Mo6+ configuration. %0 journal article %@ 0925-4005 %A Silva, E.,Bastos, A.C.,Neto, M.,Fernandes, A.J.,Silva, R.,Guerreiro, M.,Ferreira, S.,Zheludkevich, M.,Oliveira, F. %D 2014 %J Sensors and Actuators B %N %P 544-551 %R doi:10.1016/j.snb.2014.07.127 %T New fluorinated diamond microelectrodes for localized detection of dissolved oxygen %U https://doi.org/10.1016/j.snb.2014.07.127 %X The present work reports on a novel needle type oxygen microsensor based on boron doped diamond (BDD) with tailored surface aiming in better electrochemical performance. The microelectrodes are produced by growing diamond films using HFCVD (hot filament chemical vapor deposition) on top of electrochemically sharpened tungsten filaments. The diamond is functionalized using CF4 RF-plasma post-treatments resulting in fluorine termination of the surface.,The quantitative detection of the dissolved oxygen (DO) is demonstrated and supported with successful fitting to the theoretical values calculated for diffusion limited current on hemicylinder shape electrode. The developed MEs were calibrated and tested as probes for microamperometric mapping of dissolved oxygen in a Zn–Fe wire-electrode model galvanic couple immersed in 50 mM NaCl. Modified diamond MEs show a fast and stable response towards oxygen mapping, as well as stability for several days of measurements. %0 journal article %@ 0370-1972 %A Salak, A.N.,Zhaludkevich, A.L.,Ignatenko, O.V.,Lisenkov, A.D.,Yaremchenko, A.A.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2014 %J Physica Status Solidi B %N 6 %P 1192-1196 %R doi:10.1002/pssb.201451013 %T High-pressure induced phase formation in the CuGaS2–CuGaO2 chalcopyrite–delafossite system %U https://doi.org/10.1002/pssb.201451013 6 %X Phase formation under high pressure in the chalcopyrite–delafossite system has been studied at 5 GPa and 500–1000 °C. The parent chalcopyrite composition used in this study was slightly Cu-deficient, corresponding to the chemical formula (Cu,Ga)0.905GaS2. It was revealed that under high-pressure and high-temperature conditions, a mixture of the parent phases partly decomposes to form Cu2S and Ga2O3. The defect chalcopyrite (Cu,Ga)0.905GaS2 splits into a near-stoichiometric CuGaS2 and a Cu-deficient cubic (sphalerite-like) phase of the (Cu,Ga)0.8S composition. Such a phenomenon has been considered in terms of characteristic features of chalcopyrite and sphalerite crystal structures. Delafossite CuGaO2 at 5 GPa and 1000 °C was found to recrystallize entirely, which results in the disappearance of the stacking faults in its layered structure. %0 journal article %@ 1463-9076 %A Serdechnova, M.,Ivanov, V.L.,Domingues, M.R.M.,Evtuguin, D.V.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2014 %J Physical Chemistry Chemical Physics %N 45 %P 25152-25160 %R doi:10.1039/c4cp03867c %T Photodegradation of 2-mercaptobenzothiazole and 1,2,3-benzotriazole corrosion inhibitors in aqueous solutions and organic solvents %U https://doi.org/10.1039/c4cp03867c 45 %X The photochemical degradation of 2-mercaptobenzothiazole (MBT) and 1,2,3-benzotriazole (BTA) inhibitors was studied in the present work in aqueous and in organic solutions. The extent of photodegradation was assessed by UV-Vis spectroscopy and the main reaction products were identified by tandem electrospray ionization mass spectrometry (ESI-MS/MS). The analysis of degradation products upon UV irradiation revealed the predominant formation of dimeric compounds from MBT and oligomeric structures from BTA, which were further converted into aniline. The increase of the quantum yield of MBT and BTA photodegradation reactions under aerobic conditions both in aqueous and organic solvents was explained by an increase of the spin–orbit conversion of the singlet radical pairs into the triplet radical pairs in the presence of oxygen. These triplet pairs further dissociate into free radicals, or convert to the parent compounds. At the early stage of UV irradiation, free radical coupling leads essentially to dimer formation in the case of MBT and to the formation of oligomers in the case of BTA irradiation. %0 journal article %@ 0034-6748 %A Silva, E.L.,Silva, R.F.,Zheludkevich, M.,Oliveira, F.J. %D 2014 %J Review of Scientific Instruments %N 9 %P 095109 %R doi:10.1063/1.4895639 %T Novel electrochemical method of fast and reproducible fabrication of metallic nanoelectrodes %U https://doi.org/10.1063/1.4895639 9 %X A novel electrochemical wire etching method of fabrication of ultrasharp nanoelectrodes is reported. Tungsten wires can be sharpened to less than 10 nm tip radius in a reproducible manner in less than 1 min by using controllable hydrodynamic electrolyte flow combined with optimized electrochemical etching parameters. The method relies on the variations of the electric field at the surface of a metal wire, while the electrolyte solution is in motion, rather than on the ionic gradient generated in a static solution. %0 journal article %@ 1463-9076 %A Shilyaeva, Y.I.,Bardushkin, V.V.,Gavrilov, S.A.,Silibin, M.V.,Yakovlev, V.B.,Borgardt, N.I.,Volkov, R.L.,Smirnov, D.I.,Zheludkevich, M.L. %D 2014 %J Physical Chemistry Chemical Physics %N 36 %P 19394-19401 %R doi:10.1039/C4CP02436B %T Melting temperature of metal polycrystalline nanowires electrochemically deposited into the pores of anodic aluminum oxide %U https://doi.org/10.1039/C4CP02436B 36 %X The arrays of metallic nanowires are considered as promising precursors for 1D semiconductor nanostructures after appropriate treatment at temperatures close to the melting point. Therefore the melting behaviour of the metallic structures in oxide templates is a key parameter for the subsequent conversion process. The present paper focuses on understanding of the effect of mechanical stress generated during heating on the melting point of the metal nanowires deposited into the pores of anodic alumina. Extremely high local compressive stress appears due to the difference in the thermal coefficients of the oxide template and nanowires inside the pores. The effect of the composite structural parameter that may be related to the concentration of nanowires on the melting temperature has been investigated. A numerical model predicting the melting point has been developed for composites with indium, tin, and zinc nanowires. The simulation results obtained using the suggested model were compared with the experimental data. %0 journal article %@ 2046-2069 %A Maia, F.,Tedim, J.,Bastos, A.C.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2014 %J RSC Advances %N 34 %P 17780-17786 %R doi:10.1039/c4ra00826j %T Active sensing coating for early detection of corrosion processes %U https://doi.org/10.1039/c4ra00826j 34 %X A corrosion sensing coating based on specially developed polymeric microcapsules with a pH-indicator is reported. The synthesis of the microcapsules is designed in a way to ensure their optimal compatibility with the polyurethane protective coatings and to allow release of the indicator at higher pH values. The obtained polyurea microcapsules have a regular and microsized morphology and a loading content of 12 wt%. The developed sensing coating applied on aluminium and magnesium alloys is able to indicate initiation of corrosion processes through a pink coating coloration, as a result of local pH increase in the cathodic areas. %0 journal article %@ 1388-2481 %A Serdechnova, M.,Kallip, S.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2014 %J Electrochemistry Communications %N %P 51-54 %R doi:10.1016/j.elecom.2014.01.023 %T Active self-healing coating for galvanically coupled multi-material assemblies %U https://doi.org/10.1016/j.elecom.2014.01.023 %X A new “self-healing” coating concept for active corrosion protection on galvanically coupled multi-material structures is reported in the present work. The novel approach is based on the combination of two types of nanocontainers with two different inhibitors in the same coating system. The nanocontainers confer a triggered release of both inhibitors which act in a synergistic way when an aluminum alloy is galvanically coupled with carbon fiber reinforced plastic. The layered double hydroxide and bentonite were used as functional nanocarriers for 1,2,3-benzotriazole and Ce3 + inhibitors respectively. Scanning vibrating electrode technique has been applied for the monitoring of galvanic corrosion activities and kinetics of self-healing processes in confined defects. The effective inhibition of electrochemical activity in the defects on coated galvanically coupled aluminum alloy with carbon fiber reinforced plastic was demonstrated for the first time. %0 journal article %@ 1098-0121 %A Khalyavin, D.D.,Salak, A.N.,Olekhnovich, N.M.,Pushkarev, A.V.,Radyush, Y.V.,Manuel, P.,Raevski, I.P.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2014 %J Physical Review B %N %P 174414 %R doi:10.1103/PhysRevB.89.174414 %T Polar and antipolar polymorphs of metastable perovskite BiFe0.5Sc0.5O3 %U https://doi.org/10.1103/PhysRevB.89.174414 %X A metastable perovskite BiFe0.5Sc0.5O3 synthesized under high-pressure (6 GPa) and high-temperature (1500 K) conditions was obtained in two different polymorphs, antipolar Pnma and polar Ima2, through an irreversible behavior under a heating/cooling thermal cycling. The Ima2 phase represents an original type of a canted ferroelectric structure where Bi3+ cations exhibit both polar and antipolar displacements along the orthogonal [110]p and [1¯10]p pseudocubic directions, respectively, and are combined with antiphase,octahedral tilting about the polar axis. Both the Pnma and the Ima2 structural modifications exhibit a long-range antiferromagnetic ordering with a weak ferromagnetic component below TN ∼ 220 K. Analysis of the coupling between the dipole, magnetic, and elastic order parameters based on a general phenomenological approach revealed that the weak ferromagnetism in both phases ismainly caused by the presence of the antiphase octahedral,tilting whose axial nature directly represents the relevant part of Dzyaloshinskii vector. The magnetoelectric contribution to the spontaneous magnetization allowed in the polar Ima2 phase is described by a fifth-degree free-energy invariant and is expected to be small. %0 journal article %@ 0257-8972 %A Yasakau, K.A.,Carneiro, J.,Zheludkevich, M.L.,Ferreira, M.G.S. %D 2014 %J Surface and Coatings Technology %N %P 6-16 %R doi:10.1016/j.surfcoat.2014.02.038 %T Influence of sol-gel process parameters on the protection properties of sol–gel coatings applied on AA2024 %U https://doi.org/10.1016/j.surfcoat.2014.02.038 %X The present work explores effects of shelf-life, temperature and the presence of cerium nitrate additive on the protective performance of sol–gel coatings applied on AA2024. These are important parameters when industrial applicability of coating formulations is considered. The studied sol–gel system is based on a combination of metalorganic precursor titanium(IV) propoxide and hybrid epoxy silane 3-glycidoxypropyltrimethoxysilane. The synthesized sol–gel formulations without or with addition of 0.007 M Ce(NO3)3 were aged during different times at temperatures 25 °C or − 6 °C. FTIR results show that the intensities of the bands associated to Sisingle bondOsingle bondSi increase with respect to Sisingle bondOH groups during the aging process as a result of extended condensation. However, such transformations occur less rapidly at low temperature. The electrochemical impedance spectroscopy measurements clearly show that sol–gel coatings corresponding to the sol–gel aged at low temperature exhibit similar corrosion protective capabilities compared to the coating obtained without sol–gel aging. It is also observed that the protection performance of the sol–gel coatings with cerium nitrate obtained after two weeks of sol–gel aging is lower compared to the coatings without cerium additive. This effect is attributed to the enhanced reactivity of the sol–gel due to cerium(III) presence. %0 journal article %@ 2196-0216 %A Starykevich, M.,Lisenkov, A.D.,Salak, A.N.,Ferreira, M.G.S.,Zheludkevich, M.L. %D 2014 %J ChemElectroChem %N 9 %P 1484-1487 %R doi:10.1002/celc.201402130 %T Electrodeposition of Zinc Nanorods from Ionic Liquid into Porous Anodic Alumina %U https://doi.org/10.1002/celc.201402130 9 %X Electrochemical deposition of zinc nanorods into the anodic aluminium-oxide template from ionic-liquid electrolyte is reported. For the first time, the electrodeposition from an ionic liquid is performed in a porous alumina template, anodically grown on the aluminium substrate without complete removal of the barrier layer. The two-step process was applied; first, with alternating-current pulse nucleation of zinc nanoparticles on the bottom of the pores, followed by direct-current growth of the rods. The electrolyte consisted of 0.5 M ZnCl2 in choline chloride and ethylene glycol in a 1:2 molar ratiod. The resulting zinc nanorods are approximately 3 μm in length and 70 nm in diameter. The achieved fill factor of the pores is in the 70–80 % range. %0 journal article %@ 1063-7850 %A Dem'yanov, S.E.,Kalanda, N.A.,Kovalev, L.V.,Avdeev, M.V.,Zheludkevich, M.L.,Haramus, V.M.,Willumeit, R. %D 2013 %J Technical Physics Letters %N 6 %P 552-555 %R doi:10.1134/S1063785013060199 %T Dielectric barrier formation and tunneling magnetoresistance effect in strontium iron molybdate %U https://doi.org/10.1134/S1063785013060199 6 %X A comparative X-ray diffraction study of the initial single-phase metal-oxide compound-strontium iron molybdate Sr2FeMoO6 − δ (SFMO)-and that subjected to additional isothermal annealing shows that this heat treatment leads to the appearance of a SrMoO4 (SMO) phase. Small-angle neutron scattering measurements indicate that the SMO phase forms a dielectric shell surrounding SFMO grains, which has a characteristic thickness of 2–4 nm and extends above 120 nm. The character of the temperature dependence of the electric resistance corresponds to the metal-type conduction in single-phase SFMO and changes to a semiconductor type in the material with SMO dielectric shells, which is evidence of a tunneling mechanism of charge transfer. This conclusion is confirmed by an increase in the absolute value of the negative magnetoresistance of SFMO due to the appearance of a tunneling magnetoresistance component of the same sign. %0 journal article %@ 0370-1972 %A Kalanda, N.A.,Kovalev, L.V.,Zheludkevich, M.L.,Haramus, V.M.,Willumeit, R.,Sobolev, N.A. %D 2013 %J Physica Status Solidi B %N 4 %P 825-830 %R doi:10.1002/pssb.201200888 %T Charge transfer processes and magnetoresistance in strontium ferromolybdate with dielectric barriers %U https://doi.org/10.1002/pssb.201200888 4 %X The Sr2FeMoO6−δ compound attracts the attention of researchers due to a high Curie temperature, large values of negative magnetoresistance at room temperature and a practically 100% spin polarization of conduction electrons. We have studied the role of grain boundaries on the electrical transport in Sr2FeMoO6−δ in applied magnetic fields up to 8 T. The compound was synthesized out of partially reduced SrFeO3−x, SrMoO4−y precursors (sample I). At the first oxidation stage upon annealing at 700 K in argon with a partial oxygen pressure p(O2) = 10 Pa for 15 h (sample II), the internal structure of the Sr2FeMoO5.82 grains did not change. Sample II exhibits a mixed type of electrical conduction. In a magnetic field B its resistivity decreases without changing the mixed regime of charge transport, only shifting the temperature of minimum resistivity (TmB) to lower values. At temperatures above TmB the conductivity is predominantly metallic, whereas below TmB down to 4.2 K it is of semiconductor type. The increase of the annealing time up to 30 h (sample III) brings about an increase of the resistivity and the appearance of semiconductor-type conductivity at T = 300–4.2 K, which indicates the formation of a continuous insulating interlayer between the grains. In a magnetic field, the resistivity decreases, with the conductivity changing from the semiconducting to a mixed one. In the latter case the charge transport can occur both through point metallic contacts and by means of spin-dependent tunneling across dielectric interlayers between Sr2FeMoO5.82 grains.