Influence of element Bi and MAO treatment on the corrosion resistance of magnesium implant

Mg-Bi alloy was prepared by metallurgical method and then surface treated by micro-arc oxidation (MAO) in this work. The influence of element Bi and MAO treatment on the corrosion resistance of Mg matrix was investigated. The results showed that, element Bi can obviously improve the corrosion resistance of Mg (2-3 orders of magnitude), which may be due to that the formation of Mg3Bi2 particles can refine the grain size of the Mg matrix. After MAO treatment, the corrosion resistance was further enhanced and the MAO treated Mg-Bi showed the best corrosion resistance, however the improvement of MAO coatings is not very huge (about two times of Mg-Bi alloy). Considering the nonuniform structure, easy degradation and instability of coating materials, Mg-Bi alloy without MAO treatment has a greater potential to be used as an implant material in clinics.