Tailoring the corrosion behavior and mechanism of AZ31 magnesium alloys by different Ca contents for marine application

The microstructure of AZ31 magnesium alloy was modified by Ca addition. AZ31-Ca alloys with refined microstructure exhibited significantly enhanced corrosion resistance in artificial seawater. AZ31–0.5Ca showed the lowest corrosion rate of 0.716 ± 0.186 mm y −1 , which was about 7.4 times lower than that of AZ31 alloy (5.326 ± 0.652 mm y −1 ). The dominant role in the reduced corrosion rates of AZ31-Ca alloys gradually changed from the compact corrosion products film containing Al 2 O 3 and CaCO 3 to the corrosion barriers consisting of net-like (Mg, Al) 2 Ca phases as the Ca content increased from 0.1 wt% to 1.5 wt%. • The AZ31-xCa (x = 0.1, 0.5, 1.0, 1.5) Mg alloys exhibited enhanced corrosion resistance in artificial seawater. • The corrosion resistance of Ca-containing AZ31 alloys presented variations of three periods. • The dense surface film containing Al 2 O 3 and CaCO 3 was the decisive factor when the Ca content did not exceed 0.5 wt%. • The barriers effect of the net-like (Mg, Al) 2 Ca phases dominated corrosion as the Ca content reached 1.5 wt%.