7020铝合金在Cl^(-)环境下的应力腐蚀与局部腐蚀性能及其相关性分析

Stress Corrosion Cracking and Localized Corrosion Properties of 7020 Aluminum Alloy under Cl^(-) Environment and Their Correlation Analysis

为进一步加深对铝合金在Cl-环境下腐蚀行为的认识,通过浸泡试验、金相分析、极化曲线测试、慢应变速率拉伸测试、扫描电镜、透射电镜观察等,研究腐蚀环境对7020铝合金的局部腐蚀和应力腐蚀开裂(SCC)行为的影响,并对二者的相关性进行分析。结果表明:7020铝合金在50℃下的3.5%NaCl溶液中浸泡24 h,合金局部腐蚀敏感性很小;在3.5%NaCl+0.5%H2O2溶液中浸泡24 h,合金局部腐蚀敏感性增大。在50℃条件下,与3.5%NaCl溶液比较,合金在3.5%NaCl+0.5%H2O2溶液中的应力腐蚀敏感性较小。由于外部环境差异,7020铝合金在Cl-浓度不变情况下,其局部腐蚀与应力腐蚀并没有特定相关性。

In order to further recognize the corrosion behaviors of aluminum alloy in Cl- -contained environment,the means of immersing experiment,metallographic observation, polarization curves measurement, slow strain rate tension, scanning electron microscope and transmission electron microscope were employed to study the localized corrosion,stress corrosion cracking( SCC) performance and the correlation between the localized corrosion and the stress corrosion of 7020 aluminum alloy. Results showed that 7020 aluminum alloy had little local corrosion sensitivity immersed in 3.5% NaCl solution at 50 ℃ for 24 h. On the contrast,the local corrosion sensitivity increased when the sample was immersed in 3.5% NaCl +0.5% H2O2 solution at 50 ℃ for 24 h. Moreover,the stress corrosion sensitivity of the alloy in 3.5% NaCl + 0.5% H2O2 solution was lower than that of the 3.5% NaCl solution at 50 ℃ . Due to the difference of the external environment,there was no specific correlation between the localized corrosion and the stress corrosion of 7020 alloy when the Cl-concentration was constant.