Duplex plasma electrolytic oxidation/ hydroxyapatite- polydopamine coating on WE43 alloy for bone implants: Long-term corrosion resistance and biological properties

Abstract

This study aims to evaluate the corrosion behavior of WE43 alloy with plasma electrolytic oxidation (PEO)/hydroxyapatite (HA)-polydopamine (PDA) duplex coating. HA-PDA is co-deposited as the top layer using an electrodeposition process by varied dopamine hydrochloride concentration and deposition time following the PEO process. The findings show the development of a corrosion-resistant coating by regulating the surface morphology. Furthermore, long-term electrochemical impedance spectroscopy reveals that the total impedance of the optimized PEO/HA-PDA coating (deposition time = 10 min and dopamine hydrochloride concentration = 1 mg/mL) increased from 1720 Ω on day 1 to 14,600 Ω following 21 days of immersion. Co-deposited HA-PDA shows less hydrogen release and higher adhesion strength than PEO/HA samples. Finally, the PEO/HA-PDA coating is desirable for magnesium bone implants by considering the bioactivity of the coating resulting in improved cell-surface interaction.