Evaluation of a simple microstructural-electrochemical model for corrosion damage accumulation in microstructurally complex aluminum alloys

Abstract

Stereological and electrochemical data collected in 0.1 M NaCl is presented for the intermetallic particles found in AA7075-T651. These values are used as inputs for a mechanistic-based corrosion model which yields a distribution of pit radii (assuming hemispherical pitting) as function of immersion time. With an optical profilometer (OP), a distribution of damage depths were collected from samples exposed to 0.1 M NaCl solution for times ranging from 10 to 1344 h. Damage depths were compared with the model predictions of pit depth. The model is able to predict observations of corrosion damage depths to within a factor of two, but tends to under-predict damage depth at short times and over-predict at long times. Under-prediction may be associated with early rapid dissolution of active particles. Over-prediction by the model at longer exposure times may be associated with the fact that repassivation is not included as a part of this simple model.