海洋大气环境下铝合金的腐蚀本质上是薄液膜下的电化学腐蚀,与本体溶液中的腐蚀有很大不同,腐蚀速率与薄液膜的厚度及成分有关。建立并实验验证了薄液膜厚度、大气相对湿度和铝合金表面盐沉积量3者之间的关系,研究7B04铝合金在不同厚度和不同NaCl浓度薄液膜下的电化学性能。结果表明,薄液膜下7B04铝合金的自然腐蚀电位较本体溶液中更容易达到稳定,且电位更正,自然腐蚀速率更大；液膜厚度减小,7B04铝合金阴极极化电流密度增加,阳极反应受到抑制；薄液膜中NaCl浓度升高,7B04铝合金的自然腐蚀电位降低,腐蚀速率上升,而阴阳极极化过程受NaCl浓度变化影响不大,当NaCl质量分数达到5%后,自然腐蚀电位基本不再变化。
The corrosion of aluminum alloy in marine atmospheric environment was an essential electrochemical corrosion under thin e-lectrolyte film, which was different from the corrosion in bulk solution, the corrosion rate was related to the thickness and composition of thin electrolyte film. The relationship among film thickness, relative humidity and salt deposit on aluminum alloy surface was estab-lished and verified by experiment. The electrochemical properties of 7B04 Al-alloy under thin electrolyte film with different thickness and different NaCl concentration were studied. The results indicate that the free-corrosion potential of 7B04 Al-alloy under thin electro-lyte film is easier to reach steady state than that in bulk solution, both free-corrosion potential and corrosion rate are higher under thin electrolyte film. With the decrease of film thickness, the cathodic polarization current density of 7B04 Al-alloy increases, and the an-ode reaction is suppressed. With the increase of NaCl concentration in thin electrolyte film, the free-corrosion potential of 7B04 Al-al-loy decreases, and the corrosion rate increases, but the polarization of the anode and cathode have little effect on the change of NaCl concentration. The free-corrosion potential of 7B04 Al-alloy is no longer changed when the mass fraction of NaCl reaches 5%.
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