微弧氧化处理对AA7075铝合金在3.5％ NaCl溶液中局部腐蚀行为的影响

摘要

采用微弧氧化法在AA7075铝合金上生成氧化铝膜层,并对氧化铝膜层在3.5％NaCl溶液中的腐蚀和应力腐蚀开裂行为进行测试.采用电化学阻抗谱来研究膜层随浸泡时间的变化,构建合适的等效电路图.对常载荷应力腐蚀开裂测试后的试样进行金相观察.结果表明,微弧氧化膜可以有效避免富Cu、Fe金属间化合物相引发的严重局部腐蚀而导致的合金过早失效.%Alumina coating was formed on AA7075 aluminum alloy by micro arc oxidation (MAO) method and its corrosion and stress corrosion cracking (SCC) behaviors were examined in 3.5％ (mass fraction) NaCl solution.Electrochemical impedance spectroscopy (EIS) was used to evaluate the degradation of the coating as a function of immersion time and was modeled with appropriate equivalent circuits.Constant load stress corrosion cracking (SCC) results followed by post-test metallographic observations demonstrated the usefulness of MAO coating to avoid the premature failure of the alloy due to severe localized corrosion initiated by Cu- and Fe-rich intermetallic phases.