In-vitro corrosion and bioactivity behavior of tailored calcium phosphate-containing zinc oxide coating prepared by plasma electrolytic oxidation

[Display omitted] •Calcium phosphate-containing coatings were prepared on the pure Zn substrate by an in-situ PEO process.•A new electrolyte composition containing C4H6O4Ca and CaHPO4 as additives was used.•By increasing the electrolyte concentration, the coatings featured excellent hydrophilic behavior.•At the optimum electrolyte concentration of C4H6O4Ca and CaHPO4, the best in-vitro corrosion resistance was achieved.•Outstanding in-vitro bioactivity and biodegradability were found for the coating prepared at the optimum condition. Calcium phosphate-containing coatings were prepared on pure zinc substrate by an in-situ plasma electrolyte oxidation process in the electrolyte containing C4H6O4Ca and CaHPO4 additives for generation biodegradable implants. The polarization test and electrochemical impedance spectroscopy indicated excellent resistance properties of the outer porous and inner barrier layers for the coating with higher thickness prepared at optimum electrolyte concentration. In-vitro bioactivity evaluation revealed that the cube-shaped particles consisting of Ca3(PO4)2, Zn3(PO4)2 and CaCO3 phases were observed for the optimized sample after soaking in simulated body fluid up to 28 days. This coating indicated the smallest pH and lowest degradation rate.