Improving Biodegradable Mg-Zn(-Ca) Alloys by Surface Treatment via Plasma Electrolytic Oxidation

This study investigated the influence of plasma electrolytic oxidation (PEO) preparation time on the degradation resistance of Mg-1Zn (Z1) and Mg-1Zn-0.4Ca (ZX10) alloys, with comparisons to pure Mg and commercial Mg-4Y-3RE-0.4Zr (WE43). PEO layers were formed with varying preparation times (5, 10, and 15 min) and analyzed for microstructure, morphology, and corrosion resistance. The results indicated that PEO layers with a 10 min preparation time had the most homogeneous structure and optimal corrosion resistance. Prolonged PEO preparation times increased pore density, crack formation, and layer thickness while also promoting layer degradation during extended immersion in 0.9% NaCl corrosive media. The dissolution of phosphates from PEO layers contributes to the formation of a protective corrosion layer, enhancing long-term resistance. These findings demonstrate that low-alloyed, biocompatible Mg-Zn(-Ca) alloys can achieve corrosion resistance comparable to high-performance WE43 alloys through appropriate surface treatment.