Yang, Shanghui, Luo, Xia, Li, Minyu, Cai, Huawei, Liu, Jiaxing, Lv, Chunyang, Huang, Jing, Bao, Feifei, Fan, Zhou, and Huang, Bensheng
Magnesium alloys are used as bone implants because of their good biocompatibility and degradability. However, due to the rapid and uneven degradation, its clinical application is limited. To improve the corrosion resistance of medical magnesium alloys, a novel technique of semisolid powder molding was used to prepare Mg-6Zn alloy, and then microarc oxidation (MAO) was firstly applied to modify the surface. In this study, the effects of different current densities (4, 6, 8 A/dm2) and microarc oxidation time (8, 14, 20 min) on the phase composition, thickness, density, microstructure, roughness, and corrosion resistance of MAO film were systematically studied, and then the optimized parameters were obtained. Finally, the optimized coating's biocompatibility (cytotoxicity, cell adhesion, hemolysis, osteogenic differentiation) was evaluated. The results show that the MAO film mainly comprises α-Mg, MgO, and Mg2SiO4. The film’s roughness, microhardness, and thickness increase with the current density and oxidation time. The lowest electrochemical corrosion rate of the coating is (2.3 ± 0.5 × 10–4mm/year under the parameter of 6 A/dm2-20 min, which decreases by about 3 orders of magnitude compared with naked Mg-6Zn (0.32 ± 0.06 mm/year). The optimized microarc oxidation parameter is 6 A/dm2-20 min, with a thickness of 18 ± 1.45 μm, and microhardness of 339.6 ± 9.09 HV (increases by 165.3%). Additionally, the cytotoxicity and hemolysis rate of naked and coated Mg-6Zn were reduced, but the cell viability and adhesion as well as the differentiation of osteoblast cells of coated Mg-6Zn were improved, exhibiting better biocompatibility. Therefore, semisolid powder molding can be used to prepare medical Mg alloys with high performance, and MAO improves corrosion resistance greatly.