Electrochemical behavior and corrosion mechanism of anodized 7B04 aluminum alloy in acid NaCl environments

Electrochemical behavior and corrosion mechanism of anodized 7B04 aluminum alloy under acid NaCl immersion and salt spray tests (pH = 3.5) were studied by morphology observation, electrochemical im-pedance spectroscopy (EIS), and scanning Kelvin probe (SKP). The influences of exposure conditions and sealing treatment on the properties of anodic film were analyzed. The results showed that the surface Volta potential distribution of 7B04 aluminum alloy tends to be uniform after anodizing and sealing treatment. In the two corrosive environments, the porous layer of both unsealed and sealed anodic film had the self-sealing process and autocatalytic process, which made the porous layer maintain high resistance in long-term tests. The sealing treatment effectively improved the blocking performance of the porous layer, and the fitted resistance value was always greater than 10(4) Omega.cm(2). The corrosion of both unsealed and sealed anodic film samples in the immersion test was more serious than that in the salt spray test, which due to the different interaction modes between the electrolyte and anodic film surface. The results of EIS, SKP, and morphology observation had a good qualitative correlation. (C) 2021 Elsevier B.V. All rights reserved.