EFFECT OF Sn ON CORROSION PROPERTIES OF HOMOGENIZED Mg-6Zn-0.25Ca MAGNESIUM ALLOY

Effect of Sn on the corrosion properties of a homogenized Mg-6Zn-0.25Ca alloy was investigated. The corrosion resistance of ZX60 and ZXT601 alloys was analyzed using XRD, metallography, SEM, mass loss, hydrogen evolution, electrochemical polarization curve and impedance spectrum. The results indicate that Mg-6Zn-Sn-0.25Ca alloy is mainly composed of CaMgSn and MgZn2 phases. After an addition of Sn, the grains are significantly refined, and the volume fraction of the second phase with disperse distribution increases. MgZn2 phase precipitates as well. The addition of Sn can significantly improve the corrosion resistance of Mg-6Zn-0.25Ca alloy, which is mainly due to the smaller grain size, as well as uniformly and densely distributed CaMgSn phase of ZXT601 alloy. Therefore, the passive film formed in the corrosion process is more uniform. The corrosion resistance of ZXT601 alloy is much higher than that of ZX60 alloy.