7150铝合金剥蚀行为及腐蚀机理研究

EXFOLIATION CORROSION BEHAVIOR OF 7150 Al ALLOY

研究了T6、T73及RRA处理(175℃回归)7150铝合金在EXCO溶液中的剥落腐蚀行为、η相与铝基体的电化学偶合行为及其相应的腐蚀机理.结果表明,7150-T6铝合金中η相在晶界连续分布,存在一个由晶界阳极性的η相与其边缘铝合金基体组成的腐蚀电偶而形成的腐蚀活性通道,导致7150-T6铝合金具有最大的晶间腐蚀敏感性及剥蚀敏感性;而T73及RRA处理导致7150铝合金晶界η相聚集而分布不连续,因而其晶间腐蚀及剥蚀敏感性大幅度降低.7150-RRA(175℃回归3小时)铝合金耐蚀性与7150-T73接近;7150铝合金中η相自腐蚀电位负于铝基体电位,其自腐蚀电流大于铝基体自腐蚀电流,在7150铝合金腐蚀过程中作为阳极而发生阳极溶解.

The exfoliation corrosion behavior of 7150 Al alloy after treatments of T6,T73 and RRA（with retrogression at 175℃ ） was investigated. The electrochemical behavior of a simulated η（ MgZn2 ） precipitate in NaCl solution and the coupling behavior of the coupled system of η-phase and Al-matrix were examined. The corrosion morphology of a simulated Al alloy with qq-phase particles was also observed. The results show that 7150-T6 Al alloy possesses great sensitivity to exfoliation corrosion ,7150-T73 Al alloy has low susceptibility to exfoliation corrosion, which is close to that of 7150-RRA Al alloy with retrogression at 175℃ for 3 h. The corrosion potential of η precipitate in 7150 Al alloy is negative with respect to that of Al matrix, and its corrosion current density is greater. Therefore, the precipitate serves as anodic phase and anodic dissolution occurs on its surface. The precipitate is distributed continuously along the grain boundary of 7150-T6 Al alloy,and there exists an active corrosion path resulting from the galvanic action between precipitates and their adjacent Al matrix, resulting in its greatest sensitivity to intergranular corrosion and exfoliation corrosion. The precipitate of the T73 and RRA treated 7150 Al alloys is distributed discontinuously at the grain boundary, and their susceptibility to intergranular corrosion and exfoliation corrosion is greatly lowered.