Modeling pit initiation rate as a function of environment for Aluminum alloy 7075-T651

Pit initiation in AA7075 was characterized by measuring metastable pits from potentiostatic testing. Environmental conditions included a range of temperatures (0-60°C), chloride concentration (0.01-0.6 M), electrolyte pH (2.5-10) and electrochemical potential (E). Metastable pit initiation rate, λ, was shown to have a dependence on all environmental variables, which is highly relevant to practical service. As a result of the wide variation in λ, an artificial neural network (ANN), rather than a deterministic model, was utilized to model λ as a function of environment. Additionally, the significant body of results herein sheds light on the general pitting characteristics of such high strength Al-alloys in a quantitative sense - whereby T, pH, and [Cl ^-] were all deemed significant parameters in accurately determining λ.