2A12-T4铝合金长期大气腐蚀损伤规律

在海南省万宁地区开展了2A12-T4铝合金暴露7年、12年和20年的大气腐蚀试验,根据腐蚀特征将腐蚀区域划分为单侧腐蚀区和双侧腐蚀区,以结构最小剩余厚度值作为腐蚀特征量,进行了不同年限试验件中不同腐蚀区域最小剩余厚度的测量和统计分析,确定了满足99.9%可靠度与95%置信度的最小剩余厚度值以及95%置信度下的最小剩余厚度置信区间,并开展了腐蚀损伤形貌的金相分析。研究结果表明:2A12-T4铝合金大气腐蚀特征量服从正态分布;在大气腐蚀7~20年间2A12-T4铝合金板件的最小剩余厚度值是线性减小的;2A12-T4铝合金大气腐蚀7年后处于点蚀、晶间腐蚀、剥蚀的过渡期,12年后发生全面剥蚀,20年后剥蚀已相当严重且伴随着点蚀;双侧腐蚀区与单侧腐蚀区相比腐蚀深度更大且剥蚀层剥落严重。

Damage rule of 2A12-T4 aluminum alloy with long-term atmospheric corrosion

Atmospheric corrosion tests on 2A12-T4 aluminum alloy are carried out in Wanning, Hainan province for 7 years, 12 years and 20 years. According to the difference of corrosion characteristics, corrosion regions are divided into one direction corrosion region and cross directions corrosion region. Using the minimum value of plate thickness as corrosion characteristic quantity, the minimum thicknesses of different regions on different specimens are measured, and a statistical study of the minimum thickness for these regions is carried out. The minimum values of plate thickness with reliability 99.9% and confidence 95% are obtained, and the confidence intervals of the minimum thickness with confidence 95% are determined. Furthermore, the corrosion damage morphologies of different regions on different specimens are studied by metallographic method. The results show that the corrosion characteristic quantity of 2A12-T4 in atmospheric corrosion environment is in conformity with normal distribution. The minimum thickness of 2A12-T4 plate decreases linearly from 7 years to 20 years. The 2A12-T4 is in a transition period of pitting to intergranular corrosion to exfoliation corrosion after 7 years atmospheric corrosion. Total exfoliation corrosion occurs on specimens exposed for 12 years, and severe exfoliation corrosion with pitting can be found on specimens exposed for 20 years. Compared with one direction corrosion region, cross directions region corrodes deeply and peels significantly.