结构缝隙宽度对6A01-T5铝合金腐蚀行为的影响

Effect of Structural Gap Width on Corrosion Behavior of 6A01-T5 Aluminum Alloy

目的研究6A01-T5铝合金缝隙腐蚀行为规律,为6A01-T5铝合金缝隙腐蚀的防治提供理论依据。方法采用常温常压浸泡法对缝隙深度恒定、缝隙宽度不同的6A01-T5铝合金缝隙腐蚀试样在碱性Na Cl溶液中进行不同时间的腐蚀试验,采用数码相机、扫描电子显微镜(SEM)和X射线衍射仪(XRD)检测分析腐蚀后试片宏观形貌、腐蚀产物形貌和成分,采用白光干涉仪检测试片表面微观轮廓和腐蚀坑深度,采用电子天平检测腐蚀失重。结果缝隙宽度为0.15mm和0.3mm的试片沿缝口产生腐蚀沟,并在缝内产生局部腐蚀坑,浸泡45 d后腐蚀沟宽度和最深腐蚀坑深度分别约为2500μm、60μm,和1200μm、80μm。而缝隙宽度为0.5 mm的试片在缝口处并未检测到明显的腐蚀沟,腐蚀45 d后最深腐蚀坑深度约40μm;试片腐蚀失重随腐蚀时间的延长呈上升趋势,且在腐蚀过程中均表现为缝隙宽度为0.3 mm的试片腐蚀失重最大,缝隙宽度为0.15 mm的试片次之,缝隙宽度为0.5 mm的试片最小。结论在碱性Na Cl溶液中,6A01-T5铝合金缝隙腐蚀程度随缝隙宽度的增加呈先增大后减小的趋势,并随腐蚀时间的延长腐蚀程度逐渐上升;缝隙腐蚀会在缝口处产生沿缝口方向的腐蚀沟,并随着缝隙宽度的增加腐蚀沟孕育周期延长,腐蚀沟宽度减小,当缝隙宽度达到0.5 mm时,不再产生明显的腐蚀沟。

There are a large number of riveted and bolted connections in engineering applications,which creates many structural gaps.These gaps can easily cause crevice corrosion and structural failure.Therefore,the work aims to provide guidance for the prevention and optimization on the gap structure to study the crevice corrosion behavior of 6A01-T5 aluminum alloy.The specimens of 6A01-T5 aluminum alloy with constant gap depth and different gap widths were subject to corrosion tests in alkaline NaCl solution for different time by immersion method at room temperature and atmospheric pressure.Optical microscope,scanning electron microscope(SEM)and X-ray diffraction(XRD)were used to analyze the morphology and composition of corrosion products.The white light interferometer was used to detect the surface microstructure and depth of corrosion pit after the removal of corrosion products,and the electronic balance was used to detect the corrosion weight loss.After 4 d of corrosion,there was obvious discoloration on the surface of the specimen.After 18 d,there was an obvious discoloration band along the direction of the gap.At the same time,there was white product adhered to the gap.After 45 d,the surface corrosion of the specimen was further aggravated,and the white corrosion products in the gap and the gap width increased significantly.The main corrosion products were Al(OH)3,Al2O3 and AlO(OH).According to the microscopic profile detection of the specimens,the specimens with gap widths of 0.15 mm and 0.3 mm produced a concave channel in the direction of the slit,and local thinning and corrosion pits were generated in the slit.After 45 d of corrosion,for the specimen with a gap width of 0.15 mm,the width of the sunken channel was about 2500μm,the depth was about 3-4μm,and the deepest corrosion pit was about 60μm.For the specimen with a gap width of 0.3 mm,the width of the sunken channel was about 1200μm,the depth was about 3-4μm,and the deepest corrosion pit was about 80μm.However,for the specimen with a gap width of 0.5 mm,no obvious sunken channel was detected at the gap,only local thinning zone and corrosion pit existed at the gap,and the deepest corrosion pit was about 40μm after 45 d of corrosion.The corrosion weight loss test showed that the corrosion weight loss of the specimen increased with the corrosion time,and the corrosion weight loss of the specimen with a gap width of 0.3 mm was the largest,followed by specimen with a gap width of 0.15 mm and the specimen with a gap width of 0.5 mm had the smallest corrosion weight loss.In alkaline NaCl solution,the gap corrosion degree of 6A01-T5 aluminum alloy increases firstly and then decreases with the increase of gap width,and gradually increases with the extension of corrosion time.The crevice corrosion will produce a concave channel along the direction of the slot opening,and with the increase of the gap width,the incubation period of the concave channel will prolong,and the width of the concave channel will decrease.When the gap width reaches 0.5 mm,no obvious corrosion concave channel will be produced.