Corrosion analysis of Al-Zn-In-Mg-Ti-Mn sacrificial anode alloy

The corrosion behaviour of Al-5Zn-0.02In-1Mg-0.05Ti-0.5Mn (wt%) alloy was investigated by SEM, EDX and TEM. The results show that there exist different corrosion types of the alloy in 3.5% NaCl solution with immersion time. At the initial stage of immersion, pitting predominate the corrosion around precipitates. The major precipitates of the alloy are MgZn2 and Al6Mn particles. The corrosion potential of the bulk MgZn2 alloy is negative with respect to that of the α-Al and the bulk Al6Mn alloy, so the MgZn2 precipitate can act as activation centre, make the aluminum oxide film breakdown and cause the pitting corrosion. In the late stage, it turns out to be a uniform corrosion due to the control of dissolution precipitation of In and Zn ions.