Research Progress on Preparation and Degradation Behavior of Micro-arc Oxidation Coatings on Medical Magnesium Alloys

Recently, magnesium alloy as a " degradable medical metal material" is more and more favored by researchers. However, the rapid corrosion degradation of magnesium alloys leads to significant mechanical attenuation and weakened suitability of the materials for bone healing, which is a bottleneck limiting its clinical application at present. As an effective measure to slow down the degradation rate of magnesium alloys, micro- arc oxidation has the advantages of simple process, high film forming efficiency and good overall performance index of the film, and realizes the dual functions of regulating the degradation rate and improving biocompatibility. In this study, based on the formation mechanism and degradation mechanism of micro-arc oxidation coatings, the research progress of micro-arc oxidation ( MAO) coatings on biomedical magnesium alloys was reviewed. The formation/rupture mechanism of micro-arc oxidation coating magnesium alloy was described in detail. The essential relationships between micro-arc oxidation process parameters and biocompatibility and coating degradation performance were systematically summarized. The growth mechanism of the self-sealing porous oxide film, the deposition process of the porous material and the reason of its retention in the micro-pores were revealed. The phase characteristics of composite surface treatment film and its degradation behavior in bionic solution environment were summarized. Finally, the future development direction of micro-arc oxidation coating for medical magnesium alloy was prospected.