7A04铝合金在薄液膜下腐蚀行为

Corrosion of aluminum alloy 7A04 under thin electrolyte layers

采用薄液膜装置研究了7A04铝合金在1mol.L-1硫酸钠溶液(pH=5)中的腐蚀行为,用扫描电镜(SEM)观察了腐蚀产物的微观形貌,用光电子能谱分析了腐蚀产物的组成,测试了试样在不同液膜厚度下腐蚀不同时间的交流阻抗曲线.结果表明:7A04铝合金在薄液膜下腐蚀不均匀,中心部位腐蚀轻微,而边沿腐蚀相对严重;腐蚀产物主要为Al(OH)3和硫酸铝;电化学阻抗谱显示在腐蚀前期(0～96h),110μm液膜下7A04铝合金的腐蚀速率最大,而在腐蚀后期(96～168h),材料在本体溶液中腐蚀速率最大.

ABSTRACT The corrosion behavior of 7A04 aluminum alloy in 1 mol· L^-1 sodium sulfate solution was investigated by a thin electrolyte layer equipment. The surface morphology was observed by scanning electron microscope （SEM）. The corrosion products were analyzed by energy dispersive X-ray detector （EDX） and X-ray photoelectron spectroscopy （XPS）. The electrochemical character of 7A04 aluminum alloy was studied by electrochemical impedance spectroscopy （EIS）. It is shown that the corrosion is not uniform, and the corrosion product at the edge is more than that at the center. The corrosion products of the specimen surface mainly are AI（OH）3 and aluminum sulfates. EIS measurements indicate that the corrosion rate of 7A04 aluminum alloy under the thin electrolyte layer of 110μm is the biggest in the initial stage （0-96 h）. But in the later stage of corrosion （96N 168 h）, the corrosion rate in the bulk solution is the biggest.