| Aluminum and aluminum alloy were widely used in the areas of aerospace aircraft, manufacturing and many fields because of its high specific strength, low density, good plasticity, excellent conductivity and high corrosion resistance etc. The corrosion resistance of ultra-high strength aluminum alloy is due to the number and distribution of second-phase precipitate which generated during solution and aging process. Therefore, reasonable treatment process can be of great significance for improving corrosion resistance of ultra-high strength aluminum alloy.In this work, laser scanning confocal microscope and scanning electron microscope were used to observe morphology of7A04aluminum alloy with different aging treatment. Salt spray corrosion test, intergranular corrosion test, exfoliation corrosion test and anodic polarization curve were used to evaluate the corrosion resistance of7A04aluminum alloy with single-ageing, two-stage aging and three-stage aging treatment. The results indicate that second-phase precipitate and impurity phase distribute around the grain boundary, both of them will dissolve in corrosion media, so that7A04aluminum alloy with continuous and huge number of precipitated phase have bad influence on the corrosion resistance of7A04aluminum alloy.7A04aluminum alloy with single-ageing treatment exhibited lowest corrosion resistance because of continuous and huge numbers of precipitated phase.7A04aluminum Alloy with two-stage aging treatment exhibited best corrosion resistance due to its discontinuous precipitated phase. The sample with three-ageing treatment shows better corrosion resistance than the one with single-ageing treatment.The corrosion behavior of the anodic oxide film on7A04aluminum alloy is investigated in this paper, where the different anodic oxide films are prepared. The electrolyte solution included boric/sulfuric mixed acid, chromic acid and oxalate/sulfuric mixed acid. The electrochemical properties and continuity of anodic oxide films are evaluated using electrochemical impedance spectroscopy (EIS) and copper sulfate test. The results indicate that the corrosion resistance of anodic film formed in boric/sulfuric mixed acid is best because of the compact anodic film, the evaluation of EIS in3.5%wtNaCl solution is310kO·cm2. The impedance of anodic film formed in boric/sulfuric mixed acid grown with increasement of oxidation time.At the same time, the impedance of anodic film formed in chromic acid is125kO·cm2, which is higher than that formed in oxalate/sulfuric mixed acid.In this paper, corrosion resistance of7A04aluminum alloy with different aging process and anodic films of the alloy was studied, the relationship between precipitate strengthen effect and corrosion resistance of7A04aluminum alloy was discussed.The corrosion resistance of diffrent oxide film obtained using several commonly anodic oxidation method was compared to determin the best anodizing method that is to improve the corrosion resistance of7A04aluminum alloy. These findings provide a reference for the actual production. |
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