Corrosion behaviour of magnesium alloys for biomedical use

Magnesium alloys attract attention as a biodegradable/bioabsorbable metallic material because of the higher strength and toughness than those of biodegradable polymers and ceramics. However, practical application of Mg alloys makes little progress due to the too rapid corrosion in physiological environments. New alloys and surface coatings are developed to improve the corrosion resistance and biocompatibility. On the other hand, in vivo corrosion rate of Mg alloys was often considerably different from that obtained with in vitro corrosion test designed for conventional metallic biomaterials such as Ti alloys. It is thus a critical issue for Mg alloys to develop appropriate corrosion evaluation methods, for that it is necessary to elucidate corrosion characteristics of Mg alloys. We examined some characteristic corrosion factors for Mg alloys using a rotating electrode, and also developed calcium phosphate coatings to control Mg alloy corrosion. In this paper, influence of various physiological corrosion factors is summarized, and corrosion behaviour of developed calcium phosphate-coated magnesium alloys is also briefly described.