Effect of Chloride Anion on Anodic Dissolution of Aluminum in 4 M NaOH Solution

Aluminum air battery is a chemical cell that provides theoretical high energy density. However the anodic dissolution rate of aluminum in 4 M NaOH solution is limited by the film formed on aluminum surface. Electrochemical measurements and scanning electron microscope (SEM) images after electrostatic polarization were used to analyze the surface structure, ionic reactions, and anodic dissolution of aluminum in 4 M NaOH. The anodic dissolution is mainly affected by aluminum oxide layer. Chloride anion suppresses the anodic dissolution below the breakdown potential. However, over the breakdown potential, chloride anion breaks down the oxide layer, and accelerates the anodic dissolution of aluminum.