Corrosion Properties of Mg-6Al-0.3Mn-aSn-bZn Alloys

The effect of addition of Sn and/or Zn on corrosion properties of Mg-6Al-0.3Mn alloy was investigated systematically by immersion and salt spray tests. In case of immersion test, average corrosion rate increased by addition of 1 wt% Sn but it decreased by addition of 1 wt% Zn. When the half of the amount of Sn addition was replaced by Zn, the average corrosion rate decreased in comparison with the average corrosion rate of Mg-6Al-0.3Mn-1Sn alloy. In case of salt spray test, the change of average corrosion rate according to composition of the alloy was similar to the result of immersion test. It seemed that the change of corrosion properties according to composition of the alloy was strongly related to the microstructural changes including the sort, fraction and morphology of second phase.