Study on the roles of bisulfite in the stress corrosion cracking of 7050-T7451 aluminum alloy in the thin electrolyte layer environment

Effect of bisulfite (HSO3-) on the stress corrosion cracking (SCC) behavior of 7050-T7451 aluminum alloy in the thin electrolyte layer environment in the presence of Cl- is investigated. Addition of HSO3- inhibits the corrosion initiation but promotes the corrosion propagation and hydrogen uptake. With a quantitative calculation, the HSO3- is demonstrated to significantly facilitate the synergistic effect between stress, corrosion, and hydrogen during the in-situ tensile test, resulting in the change of the SCC controlling step from corrosion-induced hydrogen to mechanical-electrochemical-hydrogen interactions. The buffer effect of HSO3- plays a dominant role in the HSO3--induced acceleration of the SCC degradation.