Comparative assessment of the degradation behavior of micro-alloyed MgZnGeCa alloy as orthopedic material

Magnesium (Mg) and its alloys have attracted increasing attention as biodegradable biomaterials. However, their rapid corrosion rates and localized degradation behavior severely restrict their clinical applications. Alloying, particularly micro-alloying, has emerged as an effective strategy to tailor corrosion behavior while maintaining favorable mechanical and biological properties of Mg. In this study, the degradation behavior of a micro-alloyed Mg0.5Zn0.2Ge0.05Ca alloy was systematically investigated in comparison with high-purity Mg (HP Mg), Mg2Zn0.2Ca and Mg2Zn0.5Y1Nd (ZE21) alloys. The results demonstrate that Mg0.5Zn0.2Ge0.05Ca alloy exhibits slow and uniform degradation behavior in both Hanks’ solution and cell culture medium. In addition, a relatively compact corrosion product layer is formed. In contrast, Mg2Zn0.2Ca and ZE21 alloys exhibit pronounced localized corrosion. HP Mg undergoes relatively uniform corrosion and shows stable electrochemical behavior. Overall, the micro-alloyed Mg0.5Zn0.2Ge0.05Ca alloy demonstrates a slow degradation rate (< 0.3 mm/year) and uniform corrosion behavior, due to its uniform microstructure and low content of secondary particles, making it a promising candidate for biodegradable Mg-based biomaterials.