Effects of pre-corrosion on mechanical properties of 7B50-T7751 aluminum alloy in sodium chloride solution

The effects of pre-corrosion, including corrosion and stress corrosion, on the mechanical properties of 7B50-T7751 aluminum alloy in sodium chloride solution were investigated. The results revealed that coarse and discontinuously distributed grain boundary precipitates (η-MgZn₂) in the alloy resulted in decreased susceptibility to intergranular corrosion (IGC) and hydrogen embrittlement (HE). However, the mechanical properties (especially the elongation of the alloy) were significantly degraded, owing to the synergistic effect of anodic dissolution and hydrogenation associated with pre-corrosion. This degradation was exacerbated by the tensile stress. With increased exposure time, the dominant mechanism for elongation degradation transformed from anodic dissolution to HE, and the effect of the tensile stress on the degradation decreased gradually. Moreover, the Weibull function model can be used to accurately and quantitatively describe the maximum pit depth evolution of the alloy.