Electrolytic calcium phosphate/zirconia composite coating on AZ91D magnesium alloy for enhancing corrosion resistance and bioactivity

A composite coating of calcium phosphate/zirconia (CaPh/ZrO2) has been applied to the AZ91D magnesium alloy through electrolytic and annealing methods for enhancing corrosion resistance and bioactivity. The intermediate ZrO2 layer plays an important role in enhancing the adhesion strength of top CaPh layer on AZ91D as the condensation of hydroxyl bonds in Zr(OH)4 precursor, also leading to the reduction of corrosion current density down to two orders of magnitude. On the other hand, the top CaPh layer enhances much more cell adhesion and proliferation, compared with the reduced cell number on the uncoated AZ91D due to its high corrosion rate.