Long-term degradation performance and biocompatibility of plasma electrolytic oxidation coated Mg-0.45Ca-xZn alloys prepared using a fluoride-based electrolyte

Abstract

In this work, plasma electrolytic oxidation (PEO) with a fluoride-based electrolyte was performed on Mg-0.45Ca-xZn (x = 0, 0.45, 1.0, 2.0 wt%) alloys to enhance their degradation properties. These PEO coatings were composed of a porous layer and a barrier layer for alloys with Zn ≥ 0.45 wt%, while the coating on Mg-0.45Ca alloy was consisted of a dense inner layer and a porous outer layer. The content of Zn in the alloy has no significant effect on the hardness, adhesion strength and composition of the PEO coating. All coated-Mg-0.45Ca-xZn samples in this work showed decent anti-degradation properties in the simulated body fluid (SBF). Among them, PEO coatings on Mg-0.45Ca-1.0Zn and Mg-0.45Ca-2.0Zn alloys could provide excellent protection to the substrate over 3 months and exhibited good biocompatibility with Grade 0–1 of cytotoxicity, which were expected to be applied in the biomedical field. Besides, PEO process in this work enabled a high-quality coating to be formed on Mg–Ca–Zn bone screws.

Keywords

• Plasma electrolytic oxidation
• Mg–Ca–Zn alloy
• Long-term degradation performance
• Biocompatibility