pH值对2024-T351铝合金在NaCl溶液中电化学行为的影响

摘要

采用动电位极化技术结合电化学阻抗谱测量,研究了pH值对2024-T351铝合金在0.6mol·L-1 NaCl溶液中腐蚀电化学特性的影响规律.结果表明,在pH=5～7的NaCl溶液中,铝合金表面可生成稳定的氧化膜,阻抗谱出现两个容抗弧.随着溶液pH的降低,极化曲线上的阴极电流密度逐渐增加,且氧化膜厚度减薄,膜电阻和电荷转移电阻均有所降低,这表明,氧化膜的保护性能随pH的减小而降低.在酸性(pH=3)NaCl溶液中,阻抗谱变为一个容抗弧,说明铝合金表面的氧化膜难以稳定存在,基体合金直接与溶液接触,极化曲线表现出基体合金的电化学特性.%Potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) were applied to investigate the effect of pH on the electrochemical behavior of 2024-T351 aluminium alloy in 0. 6 mol o L-1 NaCl solution. The results showed that the passive film on the surface of aluminium alloy was stable in NaCl solition when pH=5～7 and the Nyquist plots were characterized by two distinct capacitance arcs. With the decrease of pH, the cathodic current density increased, the passive film became thinner, both Rox and Ret decreased. In acid (pH = 3) NaCl solution, there was only one capacitance arc in Nyquist plot, indicating that the passive film was not stable with the decrease of pH. As a result, the matrix alloy was exposed to solution directly and subject to corrosion, and the polarization curves showed the electrochemical characteristics of 2024-T351 aluminium alloy.