Effect of T4 treatment on the corrosion resistance of Mg-4Al-6Er-0.3Mn alloy

The Mg-Al alloys exhibit poor corrosion resistance when they exposed to Cl- attack. To solve this problem, Erbium (Er) and Manganese (Mn) are added to the Mg-4Al alloy and the Mg-4Al-6Er-0.3Mn is T4 treated to enhance the corrosion resistance of the alloy. Then the corrosion behaviors of the as-extruded alloy and the T4 alloy are investigated in this paper. It is found that the effective cathode Mg17Al12 is significantly reduced in the alloy due to the precipitation of Mg17Al12 being suppressed by Al2Er and the dissolution of the Mg17Al12 in the alloy. It is observed that the corrosion products transform from needle-like to tetrahedral-shaped corrosion products during the transformation process, which leads to severe pit corrosion. The results show that the T4 treatment can delay the transformation of the morphologies of the corrosion products, thereby improved the alloy corrosion resistance during the early stages of corrosion.