Abstract
7075 alloy was treated with deep cryogenic treatment (DCT) and retrogression and re-aging treatment (RRA). The corrosion behavior of the alloy was investigated by potentiodynamic polarization measurement, electrochemical impedance spectroscopy and intergranular corrosion test. The microstructure and corrosion morphology of the alloy were observed by transmission electron microscope and scanning electron microscope, respectively. The results showed that DCT could change the electrochemical corrosion process of the alloy. DCT applied to different stages of RRA treatment had a great influence on the number, size and distribution of the matrix and grain boundary precipitates. When DCT was applied after retrogression treatment, Icorr and corrosion rate of the alloy on electrochemical test was 0.006 mA cm−2 and 0.197 mm/a, respectively, and IGC depth was 25 μm. Moreover, the discontinuous grain boundary precipitates showed a better distribution state, thus corrosion resistance was remarkably improved.
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