Kritische Faktoren und Mechanismen von Korrosionsprozessen an Mg-Legierungen
Final Report Abstract
The project studied on one hand side development of novel chemical, electrochemical and biological surface functionalization methods for Mg alloys. Another focus was the detailed investigation of corrosion mechanisms of Mg alloys in simulated body environments. These two topics are partially linked, as the coatings developed were (and are) being investigated not only in view of corrosion protection but also in view of their biological performance. Optimized anodization in non-aqueous electrolytes led to formation of nanoporous or nanotubular anodic layers on Mg; such surface morphologies have previously not been reported for Mg alloys. For corrosion protection, an electrochemical route for direct coating of Mg alloys with conducting polypyrrole coating was developed. This coating acts as a weak barrier coating; the resulting corrosion protection performance can be tailored by changing the electrochemical deposition parameters. In addition, biological functionalization of Mg alloy surfaces with protein adsorption layers was investigated. A homogeneous coverage of Mg surface by albumin was achieved, using specific surface pre-treatments and silane coupling chemistry. Such an optimized albumin-layer was found to very efficiently passivate the Mg surface. Corrosion behavior of Mg alloys was studied in different types of simulated body fluid (SBF) solutions. Significantly lower corrosion rates were observed in cell culture medium than in SBF solutions. The effect of buffering of the electrolyte was recognized as one of the dominant factors in influencing surface layer formation and resulting corrosion behavior of Mg alloys. Moreover, the influence of bovine serum albumin (BSA) addition to simulated body fluids on the corrosion behavior of Mg alloys was investigated. A complex time-dependent influence on the corrosion rate was observed: in the first hours of immersion the presence of BSA in the solution decreased the corrosion rate, but during longer immersion times the dissolution rate was higher in the albumin-containing solution than in absence of albumin. Further investigations to elucidate the mechanisms of protein effects on Mg dissolution are ongoing. In vitro cell culture testing on Mg alloy surfaces was initiated, to explore the effects of Mg corrosion as well as the effects of different developed surface coatings on the biocompatibility. Preliminary electrochemical experiments on the influence of cell adhesion layers on Mg alloy corrosion were carried out.
Publications
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Time-dependent electrochemical characterization of the corrosion of the magnesium alloy WE43 in simulated body fluids. J. Biomedical Materials Research A 85A (2008) 167
R. Rettig, S. Virtanen
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Effect of acid etching and fluoride treatment on corrosion performance of Mg AZ91D alloy. Electrochimica Acta 55 (2009) 250
M.C. Turhan, R. Lynch, M.S. Killian, S. Virtanen
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Effect of surface pre-treatments on biocompatibility of magnesium. Acta Biomaterialia 5 (2009) 2783
C. Lorenz, J. Brunner, P. Kollmannsberger, L. Jaafar, B. Fabry, S. Virtanen
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Porosity Tailored Growth of Novel Black Anodic Layers on Magnesium in an Organic Electrolyte. J. Electrochem. Soc. 156 (2009) C62
J. Brunner, R. Hahn, J. Kunze, S. Virtanen
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Anodic growth of selfordered magnesium oxy-fluoride nanoporous / tubular layers on Mg alloy (WE43). Electrochemistry Communications 12 (2010) 796
M.C. Turhan, R.P. Lynch, H. Jha, P. Schmuki, S. Virtanen
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Covalent functionalization of metallic magnesium with protein layers. Langmuir 26 (2010) 12044
M. Killian, V. Wagener, P. Schmuki, S. Virtanen
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Control of magnesium corrosion and biocompatibility with biomimetic coatings. J. Biomedical Materials Research B 96 (2011) 84
S. Keim, J.G. Brunner, B. Fabry, S. Virtanen
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Electrochemical formation and characterization of polypyrrole on Mg-Al alloy (AZ91D). Synthetic Metals 161 (2011) 360
M.C. Turhan, M. Weiser, M.S. Killian, B. Leitner, S. Virtanen
