A mathematical model for the initiation of crevice corrosion was developed based on the hypothesis that, for A1 in 0.05N NaCl, initiation occurs when the concentration of dissolved metal exceeds a certain minimum critical value. This hypothesis was tested experimentally in the preceding qualitative paper. The model accounts for crevice geometry; for electrode reactions of aluminum, oxygen, and hydronium ion; for homogeneous hydrolysis equilibria; and for transport by unsteadystate diffusion and migration. The predictions of the model, made with use of literature data for all parameters, were found to compare favorably with experimental observations reported in the previous paper. The model predicts rapid depletion of O2 and rapid acidification of the crevice solution, followed by the gradual buildup of dissolved metal species which eventually trigger breakdown. The model also predicts that there is negligible accumulation of Cl− within the crevice prior to breakdown. The model accurately predicts the influence of crevice geometry upon breakdown time.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry