7050铝合金硬质阳极氧化膜热带海洋大气环境耐蚀性能研究

Corrosion Resistance of 7050 Aluminum Alloy Hard Anodic Oxide Film in Tropical Marine Atmosphere

目的研究7050铝合金硬质阳极氧化膜在热带海洋大气环境下的耐蚀性能变化规律。方法在7050铝合金表面制备硬质阳极氧化膜,然后采用不封闭、沸水封闭与铬酸盐封闭3种后处理方式进行处理。采用实验室多因素组合循环模拟试验方式与热带海洋大气环境户外直接暴露对试样开展耐蚀性能试验。通过外观、极化曲线、电化学阻抗谱方法,分析其耐蚀性能变化规律。结果硬质阳极氧化膜不封闭处理的耐蚀性较差,实验室多因素组合循环试验第1循环后表面就出现白色腐蚀产物,评级为5/2xA。户外暴露试验12个月后,不封闭处理膜层的自腐蚀电位为‒814.88 mV,自腐蚀电流密度为0.307μA/cm^(2);沸水封闭膜层的自腐蚀电位为‒717.86 mV,自腐蚀电流密度为0.177μA/cm^(2);重铬酸盐封闭膜层的自腐蚀电位为‒703.33 mV,自腐蚀电流密度为3.82×10^(-2)μA/cm^(2)。户外暴露12个月后,不封闭处理、沸水封闭处理与重铬酸盐封闭处理膜层在0.01 Hz的阻抗模值分别为1.04×10^(5)、1.51×10^(5)、4.76×10^(5)Ω·cm^(2)。结论封闭处理能提升7050铝合金硬质阳极氧化膜的耐蚀性能,且重铬酸盐封闭后的耐蚀性能优于沸水封闭后的耐蚀性能。

This paper aims to study the variation of corrosion resistance of 7050 aluminum alloy hard anodic oxide film in tropical marine atmospheric environment.The hard anodic oxide film was prepared on the surface of 7050 aluminum alloy,and then it was treated by three processes:non-sealing treatment,boiling water sealing treatment,and chromate sealing treatment.The corrosion resistance of samples was tested by laboratory multi-factor combined cycle simulation test and outdoor direct ex-posure of tropical marine atmospheric environment.The change rule of corrosion resistance was analyzed by appearance,po-larization curve and electrochemical impedance spectroscopy.The corrosion resistance of hard anodizing film without sealing treatment is poor.White corrosion products appear on the surface after the first cycle of multi-factor combined cycle test in the laboratory,and the rating is 5/2xA.After 12 months of outdoor exposure test,the self-corrosion potential of the unclosed film was‒814.88 mV,the self-corrosion current density was 0.307μA/cm^(2),the self-corrosion potential of the boiling water sealing film was‒717.86 mV,the self-corrosion current density was 0.177μA/cm^(2),the self-corrosion potential of dichromate sealing film was‒703.33 mV,and the self-corrosion current density was 3.82×10^(-2)μA/cm^(2).After 12 months of outdoor exposure,the impedance modulus of the non-sealing treatment,boiling water sealing treatment,and dichromate sealing treatment at 0.01Hz were 1.04×10^(5)Ω·cm^(2),1.51×10^(5)Ω·cm^(2),and 4.76×10^(5)Ω·cm^(2),respectively.The sealing treatment can improve the corrosion resis-tance of 7050 aluminum alloy hard anodic oxide film,and the sealing corrosion resistance of dichromate is better than that of boiling water.