Recent developments in coatings on biodegradable Mg alloys: A review

• A review of bio coatings on biomedical/biodegradable Mg alloys is provided. • Some typical surface coatings are systematically described and discussed. • It mainly focuses on the most recent relevant researches. • Existing issues and future perspective are discussed for the future study. Mg and its alloys show high potential to be applied as implant materials due to their superior properties like biodegradability, bioactivity, biocompatibility, and suitable mechanical behaviors. Nevertheless, the fast and uncontrolled degradation of Mg alloys in biological environment severely restricts their wide applications as biomedical materials. In comparison with alloying, surface coatings can not only improve corrosion resistance but also impart other bio-functional properties to achieve diverse clinical requirements. This review analyzes and summarizes the most recent developments in popular coating technologies, including micro-arc oxidation, electrophoretic deposition, chemical conversion, anodic oxidation, layered double hydroxide, and sol-gel coatings. Considering inevitable damages under complex service conditions, smart self-healing coatings are also introduced in each coating technology. The existing issues and future perspectives are finally discussed to facilitate applications of Mg alloys as biomedical materials in the medical industry.