Effect of Sn addition on the microstructure and corrosion behavior of dilute wrought Mg-Zn-Ca series alloys

The effect of Sn alloying (0.5, 1.0, 2.0 wt.%) on microstructure and corrosion behavior of dilute Mg-2Zn-xSn-0.5Ca rolled sheets is illuminated. The corrosion resistance first increases and then decreases with raising Sn content. The alloy with 1 wt.% Sn shows the lowest corrosion rate of ~2.1 mm/y, decreased by ~63% compared with Sn-free alloy. Although nobler MgSnCa phase is formed after alloying, more protective oxide film containing SnO2 is also formed, which effectively hinders localized corrosion. However, at 2 wt.% Sn addition, detrimental effect of MgSnCa overwhelms positive effect of Sn on film, thus deteriorating corrosion resistance.