7475高强铝合金在海洋和乡村大气环境中的腐蚀行为研究

目的研究海洋和乡村大气环境对7475高强铝合金腐蚀行为的影响,为7475高强铝合金环境适应性设计提供支撑。方法在万宁和北京大气环境试验站开展了7475高强铝合金为期36个月的户外暴露试验,通过腐蚀失重分析方法研究了7475高强铝合金在我国2种典型大气环境中的腐蚀动力学规律;借助环境扫描电镜(ESEM)、金相显微镜和X射线光电子能谱(XPS)等表征技术研究了7475高强铝合金的微观腐蚀形貌和锈层成分。结果2种大气环境中,铝合金腐蚀都呈现出初始阶段腐蚀迅速发展,之后腐蚀速率减慢,最后进入腐蚀扩展相对平稳时期的变化规律。在海洋大气环境中户外暴露36个月后,7475高强铝合金呈现明显的点腐蚀特征,腐蚀产物组成为Al(OH)_3、Al_2O_3和Al_2Cl_3。7475高强铝合金在乡村大气环境中表面腐蚀非常轻微,个别表面出现非常小且浅的腐蚀点。结论在乡村大气环境和海洋大气环境中,7475高强铝合金腐蚀动力学遵循幂函数规律。相比较乡村大气环境,7475高强铝合金在海洋大气环境中表现出非常强的腐蚀敏感性。

Corrosion Behavior of 7475 High-strength Aluminium Alloy in Marine and Rural Atmosphere Environments

The work aims to investigate the effect of marine and rural atmosphere environments on corrosion behavior of 7475 high-strength aluminium alloy, and provide the support for the environment worthiness design of 7475 high-strength aluminium alloy. A 36-month outdoor exposure test was carried out to 7475 high-strength aluminium alloy in Wanning and Beijing atmosphere environment test sites and the atmospheric corrosion kinetics law of 7475 high-strength aluminium alloy in two Chinese typical atmosphere environment was investigated by dint of the weight loss. The micro-morphology and the composition of the rust of 7425 high-strength aluminium alloy were studied by the environmental scanning electron microscope (ESEM), metallographic microscope and X-ray photoelectron spectroscopy (XPS). The atmospheric corrosion rate of 7475 high-strength aluminium alloy exposed in two atmosphere environments exhibited the same change law. The corrosion rate developed rapidly, then decreased with the prolongation of exposure time, and finally came to the stable stage of corrosion expansion. 7475 high-strength aluminium alloy exposed in marine atmosphere environment for 36 months exhibited obvious pitting corrosion, and the corrosion product were mainly composed of AlCl3, Al(OH)3 and Al2O3. The corrosion on the surface of 7475 high-strength aluminium alloy exposed in rural atmosphere environment was very slight and only small and shallow corrosion pits appeared on very few surface. In rural atmosphere and marine environments, the atmospheric corrosion kinetics of 7475 high-strength aluminium alloy follows the power function. Compared with rural atmosphere environment, 7475 high-strength aluminium alloy exhibited the strong corrosion susceptibility in marine atmosphere environment.