Characterization and Degradation Study of Calcium Phosphate Coating on Magnesium Alloy Bone Implant In Vitro

Magnesium alloys have similar mechanical properties with natural bone, and they degrade within a certain time span. Therefore, magnesium alloys are suitable to be made as bone screws or plates. However, high susceptibility to corrosion has limited their applications in the orthopedic field. They would possess great medical functions if the degradation rates of magnesium alloys could be reduced. This paper describes approaches to form calcium phosphate coating on magnesium alloy (AZ31) to control the degradation rate. Samples of AZ31 were placed in the supersaturated calcification solution prepared with Ca (NO₃)₂ , NaH₂PO₄, and NaHCO₃, and then, the calcium phosphate coating was formed. The composition, phase structure, and morphology of the coatings were investigated. The degradation behaviors of the naked and coated magnesium (Mg) alloys were studied in simulated body fluid. The results of this paper have shown that the coatings significantly decrease the degradation rate of the original Mg alloy, indicating that the Mg alloy with calcium phosphate coating is a promising degradable bone material.