Effect of Cl^- Concentration on the Electrochemical Behaviors of 2A12 Aluminum Alloy

The electrochemical behaviors of aluminum alloy 2A12 was investigated using alternate immersion test, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) techniques. The results showed that the corrosion process was mainly controlled by charge transfer resistance under the condition of lower Cl^- concentration after 48 h alternate immersion; with increasing the Cl^- concentration, the electrochemical characteristic changed to mixed control of charge transfer resistance and Warburg resistance. After 480 h alternate immersion, Nyquitt curves consisted of capacitance arc at high frequencies and Warburg impedance at low frequencies in 0.5% and 10% NaCl solutions, but changed into two capacitance arcs in 2.5% to 5% NaCl solutions. The increase of Cl^- concentration could promote the formation and propagation of pitting, and thus the electrochemical behavior of 2A12 aluminum alloy was affected.