Enhanced Corrosion Resistance and Mechanical Properties of Mg-Zn Alloy via Micro-alloying of Ge

Generally, the corrosion of magnesium (Mg) and its alloys is accompanied by hydrogen production, which can cause gas pockets and severe biological problems when they are used as implants. Germanium (Ge) as an alloy additive can moderate the cathodic reaction of Mg alloys and significantly delay the corrosion of Mg alloys via the cathode “poisoning” effect. In this study, the influence of Ge (0–0.75 wt.%) on the mechanical properties and corrosion resistance of Mg-0.7Zn were evaluated using electrochemical tests, weight loss experiments, and compression tests to optimize the composition of the Mg-Zn-Ge alloy having a low corrosion rate and high mechanical properties. The results show that the eutectic mixture (α-Mg + Mg2Ge) is formed in the Mg matrix after adding Ge to the Mg alloys. Small amounts of Ge addition can effectively reduce the cathodic reaction rate and improve the corrosion resistance via the cathode poisoning effect, and strengthen the mechanical properties of the alloy due to the formation of Mg2Ge. However, a relatively high content of Ge results in the formation of mesh-like precipitates, causing strong galvanic corrosion between the α-Mg matrix and secondary phases compared with the cathode poisoning effect of Ge, thereby deteriorating the mechanical properties of the alloy.