Self-adjustment of calcium phosphate coating on micro-arc oxidized magnesium and its influence on the corrosion behaviour in simulated body fluids

• Preparing temperature effects the microstructure of calcium phosphate coating.
• High temperature improves hydroxyapatite formation and elongation.
• High temperature inhibits dicalcium phosphate dihydrate deposition.
• Calcium phosphate coating changes into bonelike apatite in simulated body fluid.
• Formation and thickening of apatite improves corrosion protection for magnesium.

A calcium phosphate (Ca-Ph) coating was prepared on micro-arc oxidized magnesium using deposition method. The microstructure of the Ca-Ph coated sample and corrosion behaviour in simulated body fluid (SBF) were investigated. The results showed that the coating consisted of hydroxyapatite (HA) and dicalcium phosphate dihydrate (DCPD). Temperature significantly affected the microstructure of the coating. Increased temperature promoted HA formation but inhibited DCPD deposition. The microstructure of the Ca-Ph coating underwent self-adjustment in SBF. Bonelike apatites were formed on the coated sample, which not only increased the thickness of coating, but also improved corrosion performance of the coated sample in SBF.