Potential bioactivity of coatings formed on AZ91D magnesium alloy by plasma electrolytic anodizing.
Magnesium is a potential candidate as biodegradable orthopedic implant thanks to its remarkable mechanical properties closed to those of natural bone. But its low corrosion resistance in the body fluid is a limiting factor. By using electrolytic plasma (or microarc) anodizing process, 10-20 μm protective coatings were formed on AZ91D magnesium alloys at a constant current density of 20 mA cm(-2). The effect of a small addition of CaO (1-3 g L(-1)) to a classical electrolytic bath (made of KOH 3 mol L(-1), KF 0.5 mol L(-1), and K(2)HPO(4) 1 mol L(-1)) was studied. The anodic films, investigated by X-ray diffraction and scanning electron microscope-energy dispersive spectroscopy, show a porous structure containing crystallized Mg(OH)(2), MgO, MgAl(2)O(4), as well as Ca and P elements. The 1 g L(-1) CaO-containing electrolyte leads to morphology and composition permitting optimum corrosion behavior evaluated by stationary electrochemical measurements and impedance spectroscopy. This improvement is associated with both the appearing of a "sealing" layer and the precipitation of an outermost Ca/P-containing layer (hydroxyapatite like) in simulated body fluid. The control of the corrosion behavior of coated magnesium alloys is therefore required to enhance their potential bioactivity.
Institut Jean Lamour-UMR7198, CNRS-Nancy-Université, Vandoeuvre-Les-Nancy, France.
Thanh-Nam
TN
Vu
Delphine
D
Veys-Renaux
Emmanuel
E
Rocca
D000497:Alloys / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003343:Corrosion; D008274:Magnesium / Q000737:chemistry*; D019736:Prostheses and Implants; D013499:Surface Properties
D000497:Alloys; D020099:Coated Materials, Biocompatible; D008274:Magnesium