Intergranular corrosion mechanism of AlCu alloy: Model and experimental validation

Abstract

Intergranular corrosion poses a serious threat to equipment safety and causes significant economic losses. In this study, a theoretical model was established to quantitatively determine the relationship between intergranular corrosion sensitivity and grain boundary segregation behavior of aluminum alloys. The model took into account the solute depletion width of the anode and potential difference between the matrix and solute depletion zone. First, the impact of solute depletion regions with varying dimensions on current distribution was investigated through Laplace equation. The findings indicated that the maximum corrosion current in the vicinity of the anode exhibited a notable decline with an increase of anode size, whereas the current density in the proximity of the cathode remained largely unaltered. Subsequently, the Butler-Volmer equation of the cathode was correlated with the solute depletion zone width of the anode by using charge conservation as a bridge. The model demonstrated that the intergranular corrosion sensitivity exhibited a decline in correlation with both an increase of solute depletion zone width and a reduction of potential difference. Taken Al4Cu as a model alloy, the intergranular corrosion sensitivity factor calculated by this model could effectively predict the intergranular corrosion depth, thereby providing a new avenue for the study of intergranular corrosion behavior of aluminum alloys.