Corrosion Behavior of as-Cast Mg-6Zn-4Si Alloy with Sr Addition

The microstructure and corrosion resistance of Mg-6Zn-4Si alloy with Sr addition were studied using XRD, OM, SEM, EDS, potentiodynamic polarization and immersion testing. The results show that the morphologies and sizes of both the primary and eutectic Mg2Si in Mg-6Zn-4Si alloy can be effectively modified by the Sr additions. With the increasing amount of Sr addition, the primary Mg2Si phase experiences a decrease in the grain size with a subsequent increase. Sr significantly improves the corrosion resistance of Mg-6Zn-4Si alloy. The ternary alloy with 0.5wt%Sr has the optimal corrosion resistance, which exhibits the highest corrosion potential, the lowest corrosion current density and corrosion rate. The homogeneous dispersion of fine Mg2Si particles with Sr element is responsible for the improvement of corrosion resistance. Excessive Sr (≥1.0wt%) leads to the generation of SrMgSi new phase, which has unfavorable effects on the corrosion resistance of the alloys.