The Role of EXCO, Modified EXCO, and MASTMAASIS Environmental Exposures on Predicting Exfoliation Corrosion of the 2060-T8E30 Alloy
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2017, NACE International. In this study, corrosion response of the 2060-T8E30 alloy was analyzed in the following environments: EXCO (an immersion test in accordance with ASTM G34), modified EXCO, and modified ASTM acetic acid salt intermittent spray (MASTMAASIS), which were used to predict the alloy system's exfoliation corrosion (EFC) susceptibility. Here, results show that exposure to the first two environments failed to accurately predict EFC during seacoast exposure while the latter was successful. The final attacks in the 2060 alloy varied from solution to solution. In EXCO solution with a pH of 0.25 and chloride content of 4 M, a severe attack of EFC occurred in the 2060 alloy. In modified EXCO solution with a pH of 3.4 and chloride content of 1.1 M, intergranular corrosion was present. Pitting corrosion appeared on the 2060 alloy in MASTMAASIS environment with pH of 3 and chloride content of 1 M. Additionally, electrochemical impedance spectroscopy signature, video capture microscopy images, and scanning electron microscope images revealed the formation of a new interface on the 2060 alloy resulting from grain lifting in the EXCO solution. Here, it is shown that there is a synergistic action between the corrosion product wedging and the pressure of hydrogen gas during the grain lifting.