Aluminum-air battery is a chemical cell that provides high theoretical 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 potentiostatic polarization were used to analyze the surface structure, ionic reactions, and anodic dissolution of aluminum in 4 M NaOH with chloride solution. The anodic dissolution is mainly affected by aluminum oxide layer. Chloride suppresses slightly the anodic dissolution below the breakdown potential. However, above the breakdown potential, chloride breaks down the oxide layer. (C) 2017 The Electrochemical Society. All rights reserved.