A novel Ca-Mg-P/PDA composite coating of Mg alloys to improve corrosion resistance for orthopedic implant materials

Magnesium alloy is becoming one of the main candidates for biodegradable orthopedic implants due to its excellent biocompatibility and mechanical properties matching with natural bone. However, its rapid degradation rate hinders its clinical application. In this study, the organic (polydopamine) and inorganic (calcium phosphates) composite coating was prepared by chemical conversion and one step impregnation method to improve corrosion resistance and osteogenic differentiation for orthopedic implant materials. The formation mechanism of the coating was discussed by phase analysis and surface morphology observation. The results of anti-corrosion performance showed that the Ca-Mg-P/PDA coating greatly reduced the hydrogen evolution amount compared with WE43 alloy substrate and Ca-Mg-P coating. The biocompatibility and osteogenic differentiation ability of the coated alloys was studied, the alloy with Ca-Mg-P/PDA composite coating exhibited the best osteogenic differentiation ability in both short and long term of osteogenic differentiation.