Effect of Ca Content on Electrochemical Discharge and Corrosion Performance of Mg-6Al-1Sn Alloy Anodes for Mg-Air Batteries

This study conducted a systematic investigation on how Ca content affected Mg-6Al-1Sn alloys as anodes for Mg-air batteries in terms of their microstructure, electrochemical corrosion behavior, and discharge performance. According to the investigation results, incorporating Ca induces the formation of blocky β-Mg₁₇Al₁₂ phases containing Ca and refines the grain structure. Compared to Mg alloys without Ca, the alloys with Ca exhibit significantly improved self-corrosion resistance because the preferential enrichment of Ca at the grain boundaries within β-Mg₁₇Al₁₂ phases reduces the potential difference between β-Mg₁₇Al₁₂ phases and Mg matrix. Consequently, galvanic corrosion is mitigated, together with the effective suppression of the self-corrosion reaction of Mg anodes. Additionally, Mg alloy shows a higher anode utilization efficiency with Ca content. The combined results indicate that Mg-6Al-1Sn-0.5Ca alloy exhibits superior self-corrosion resistance and discharge properties vs. other tested compositions. Furthermore, the Mg-air battery using Mg-6Al-1Sn-0.5Ca alloy as the anode demonstrates a heavier average discharge potential and a utilization efficiency of 71.12%, which is 7.56% higher than Mg-6Al-1Sn alloy.