AbstractMg-0.5 (wt.%)Ca alloys with different microstructures are prepared through casting followed by different cooling rates. The impact of microstructure, especially second phase morphology, on self-corrosion and discharge performance of Mg-0.5Ca alloys is investigated. The water-cooled Mg-0.5Ca alloy shows a lower self-corrosion rate than the air-cooled one and enables the Mg-air cell to possess increased utilization efficiency and enhanced energy density. Intermittent discharge tests are performed to study the battery performance after no-discharge intervals. All results indicate that the water-cooled Mg-0.5Ca cast alloy could be a promising anode material for aqueous Mg-air batteries with long-term storage and under intermittent discharge.