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Séminaire Jeudi 11 Juillet 2019 - 14h - Bibliothèque de l’ICMN

Influence of Interface in Corrosion Protection of AZ31B Magnesium Alloy – Proof of Concept for Prosthetic Applications

Andrei Jitianu

  • Department of Chemistry, Lehman College, New York 10468, USA
  • Ph.D. Program in Chemistry and Biochemistry, Graduate Center of City University of New York

Summary :
Biodegradable magnesium alloys have an increasing use in orthopedic and cardiovascular applications, particularly for stents and bone implants. Magnesium and its alloys are used for biomedical applications due is its low density ( 1.8 g/cm3), close to that of the bones, high strength-to-weight ratio, good thermal and electrical conductivity and low elastic modulus. The main problem of magnesium alloys is their low stability toward corrosion. These can react with oxygen and with water producing hydrogen, which can be dangerous. Due to their high reactivity all the above mentioned properties can be lost. Preventing or controlling the rate of corrosion of magnesium alloys become an important aspect of the biomedical research. This study is a proof of concept that AZ31B magnesium alloy, which is used in prosthetic applications, can be protected efficient against corrosion using a hybrid barrier obtained by sol-gel method.
Here, we designed hybrid coatings obtained by the consolidation of organically modified polysilsesquioxanes “melting gels” for the corrosion protection of AZ31B magnesium alloy in NaCl solutions. Homogeneous and crack-free hybrid glass coatings with different thickness were obtained on AZ31 magnesium alloy by consolidation of melting gels based on methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DMDES). The main focus was to study the interaction between coatings and substrate, and the influence of the coating thickness on the final properties. Micro-scratch tests, adhesion by tape tests, confocal Raman microscopy, FT-IR spectroscopy, and SEM-EDS indicate good adhesion of coatings based on the interaction of melting gels and substrate. Those measurements indicate the presence of the Si-O-Mg bonds between the substrate and coatings. Electrochemical results show very low current densities (10-13 A cm-2) without any breakdown potential, and impedance values of 1010 Ohm cm2.