Investigating the corrosion behavior of as‐cast Mg‐Zn‐Ca alloys with the same Zn/Ca atomic ratio by in situ observation

The alloying contents with the same Zn/Ca atomic ratio of 0.13 on the corrosion behavior of Mg‐Zn‐Ca (ZX) alloys were investigated. The second phases in ZX10, ZX20, ZX30, and ZX51 alloys were identical with a majority of Mg 2 Ca and very few Ca 2 Mg 6 Zn 3 and their distribution changed from isolated to continuous state in ZX30 and ZX51. ZX10 had the lowest corrosion rate of 0.55 mm/year after 168 h immersion in simulated body fluid solution due to the smallest number of sites of galvanic corrosion. The corrosion rate of ZX30 alloy was the highest (0.72 mm/year), while though ZX51 alloy had the most Mg 2 Ca, its corrosion rate was reduced to 0.69 mm/year, resulting from the small size and thin Mg 2 Ca. In situ microstructure observation demonstrated the high fraction Mg 2 Ca phase and continuous Mg 2 Ca with bulky size were the main reason for the fast corrosion rate.