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采用浸泡实验与电化学循环极化曲线测试研究了7020铝合金在3.5%(质量分数)NaCl溶液中的点蚀行为,并结合金相显微镜(OM)、扫描电镜(SEM)及扫描透射电镜(STEM)的微观组织观察结果对相关机理进行了分析和探讨。结果表明:7020铝合金的最大点蚀深度随时间变化的曲线为S型,呈缓慢增长-快速增长-保持稳定的过程。合金中α-AlFeSiMn相在点蚀浸泡过程中充当阴极,且发生了去合金化,周围的Al基体充当阳极而被腐蚀,含MnCr的弥散相则伴随Al基体的腐蚀而脱落。浸泡后期点蚀敏感性降低,表面的腐蚀产物可起到一定的保护作用。
The pitting corrosion behavior of 7020 aluminum alloy in 3.5% NaCl solution was studied by immersion test and electrochemical cycling polarization curve. The corrosion behavior of 7020 aluminum alloy was investigated by OM, SEM and SEM (scanning electron microscopy) STEM) microstructure observation results of the relevant mechanisms were analyzed and discussed. The results show that the curve of the maximum pitting depth of 7020 aluminum alloy with time is S-shaped, showing a slow growth, rapid growth, and stable process. The α-AlFeSiMn phase in the alloy acts as the cathode during the pitting immersion process, and de-alloying occurs. The surrounding Al matrix acts as an anode and is eroded. The MnCr-containing dispersed phase exfoliates with the Al matrix. After immersion pitting sensitivity decreased, the surface of the corrosion products can play a protective effect.