Effect of Hg²⁺ Concentration in Seawater on Corrosion of Surface Modified Layer of 6063 Aluminum Alloy

The effect of heavy metal Hg²⁺ concentration on the seawater corrosion resistance of the aluminum-zinc coating was studied by immersion corrosion experiments and electrochemical means. According to the electrochemical test, it is found that as the Hg²⁺ content increases, the corrosion current gradually increases, the capacitive reactance arc presented in the high frequency region gradually decreases, and the inductive reactance disappears, indicating that the corrosion is accelerated. When the concentration is lower 0.5 μg/L, the self-corrosion potential is basically at the same level, indicating similar corrosion tendencies. However, when the content of Hg²⁺ exceeds 0.5 μg/L, the corrosion potential gradually decreases, indicating that the tendency of corrosion increases with the increase of Hg²⁺ concentration. The immersion corrosion experiment shows that with the increase of Hg²⁺ concentration, the average corrosion rate gradually increases. When the concentration is lower 0.5 μg/L, the average corrosion rate does not exceed 20 μm/a. In the Hg²⁺ concentration range of 0.5~15μg/L, the corrosion rate is basically between 20~35 μm/a.