Study on Electrochemical Behavior of 2024-T3 Aluminum Alloy in Different Acidic Aqueous Solutions

The electrochemical measurement techniques of potentiodynamic polarization and AC impedance, combined with the observation on electrode surface micro-morphology, were applied to investigate the electrochemical behavior of 2024-T3 aluminum alloy in aqueous solutions with different acids (including acetic acid, sulfuric acid and hydrochloric acid) and different pH values. Results show that with the decrease of pH value, the self-corrosion potential shifts negatively, the self-corrosion current density and the corrosion rate increase, the passivation film covering on the electrode surface is more easily damaged, and the corrosive characteristic of the solution becomes stronger. Under different pH values, the reaction course of cathodic polarization is different. When pH value is the same, the corrosive characteristic of hydrochloric acid solution is the strongest, sulfuric acid aqueous solution is close but inferior, and acetic acid aqueous solution is the weakest. This is due to the different hydrolysis ability of the acid and the presence of the chloride in hydrochloric acid solution. Because of the existence of the passivation film, the electrochemical behavior of the electrode in different corrosive environment is various. The passivation film loses the stability and dissolves under the acidic condition, so the alloy matrix is exposed and contacts with the reaction solution directly. In the weak acidic solution, the passivation film can maintain relative integrity, and have a certain protective effect on the alloy substrate.