盐雾环境下高强度铝合金的点蚀行为

采用断面金相法和局部交流阻抗技术对高强度航空铝合金7B04在连续盐雾腐蚀试验下的点蚀行为进行分析。试验结果表明，合金表面点蚀呈现腐蚀速度快速憎加，到腐蚀中期减缓，后期又急剧增加的趋势；但最大点蚀深度始终呈线性增长, 点蚀坑的形成机理主要有：阴极相粒子周围基体的溶解、铝本身的去合金化及腐蚀残留物Cu粒子的二次点蚀，其中AlCu和AlCuMg第二相粒子阴极相是其点蚀形成的诱因。局部交流阻抗技术可以提供微小区域阻抗变化的有效信息，适合用于研究点蚀发展的溶解动力学。

PITTING CORROSION OF HIGH STRENGTH ALUMINUM ALLOYS IN SALT SPRAY TEST

Salt fog spray test is used to accelerate the corrosion of 7B04 aluminum alloy. The pitting corrosion of this alloy was investigated by using metallographic method and localized electrochemical impedance spectroscopy (LEIS). It was concluded that the corrosion rate of the alloy increased sharply, but was retarded at the middle stage of exposure. The maximum depth of the pitting was linearly growing in the whole process. The pitting mechanism was mainly attributed to the dissolving the surrounding matrix of cathode-phase particles, dissolving aluminum itself or secondary pitting of Cu particles which is the corrosion residues. While the cathode phase of AlCu or AlCuMg second-phase particles was the main initiation cause. Localized electrochemical impedance spectroscopy (LEIS) which is suitable to follow changes in the dissolution kinetics during pit growth, could provide valuable information on the changes of the impedance on a small area.