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目的开展飞机用7B04铝合金缝隙腐蚀仿真研究,理解缝隙腐蚀机理,找出影响缝隙腐蚀的关键因素。方法分析缝隙腐蚀类型,开展缝隙腐蚀试验,建立缝隙腐蚀数学模型,选择合适的边界条件,利用有限元法进行仿真计算。结果缝隙内pH值分布计算结果与试验测量值一致,缝隙口与外部液体/大气连接时,缝隙内溶液分别呈酸性或碱性。缝隙口溶液电势较低,缝隙口附近的铝合金腐蚀较快,含Al腐蚀产物多集中在缝隙口附近。缝隙宽度在0.1~0.3 mm范围内变化不影响铝合金腐蚀速率;缝隙深度增加,缝隙口与底部溶液电势差增大,铝合金腐蚀面积增大,但铝合金最大腐蚀电流密度不变。电位升高,缝隙内铝合金的腐蚀加剧,电位提高10 m V,腐蚀24 h后缝隙内铝合金界面的腐蚀电流密度增加59倍,Al(OH)_2Cl的最大浓度为自然电位下的30倍。结论缝隙腐蚀主要受缝隙外部阴极还原反应影响,电位对铝合金缝隙腐蚀的影响最大,飞机结构中应避免高电位材料同铝合金直接接触。
Aim To carry out simulation research on crevice corrosion of 7B04 aluminum alloy for aircraft, understand crevice corrosion mechanism and find out the key factors affecting crevice corrosion. Methods The types of crevice corrosion were analyzed and the crevice corrosion test was carried out. The crevice corrosion mathematical model was established, the suitable boundary conditions were selected, and the finite element method was used to simulate the crevice corrosion. Results The calculation results of the pH distribution in the gap agree well with the experimental values. When the gap is connected with the external liquid / atmosphere, the solution in the gap is acidic or alkaline, respectively. The electric potential of the slot mouth solution is lower, the aluminum alloy near the slot mouth corrodes fast, and the corrosion products containing Al are mostly concentrated near the slot mouth. The change of gap width in the range of 0.1-0.3 mm did not affect the corrosion rate of aluminum alloy. The gap depth increased, the potential difference between the gap mouth and the bottom solution increased, and the corrosion area of aluminum alloy increased, but the maximum corrosion current density of aluminum alloy remained unchanged. The corrosion rate of aluminum alloy in the gap increased and the potential increased by 10 mV. The corrosion current density in the interface of aluminum alloy increased 59 times and the maximum concentration of Al (OH) 2Cl was 30 times of the natural potential . Conclusions Crevice corrosion is mainly affected by the external cathode reduction reaction of the crevice. Potential has the greatest influence on the crevice corrosion of the aluminum alloy. Direct contact between the high potential material and the aluminum alloy should be avoided in the aircraft structure.