A MATHEMATICAL-MODEL OF THE INITIATION OF CREVICE CORROSION IN METALS

A mathematical model of the evolution of the solution chemistry and electrostatic potential within a passive crevice in a metal is presented. It aims to simulate the early stages of crevice corrosion, leading to the breakdown of the passive film and local activation of the metal. The model is based on a mathematical description of the physical and chemical mechanisms controlling the process, and includes ionic migration and chemical reactions. It is used to simulate various experiments reported in the literature, both for validation purposes and to aid interpretation of the empirical results, and it has the potential for use in a predictive role. The model reproduces observed trends qualitatively in most of the cases studied, and in many cases the quantitative agreement is reasonable. The predictions were not so accurate in highly concentrated solutions characterising some of the crevice experiments. This is attributed to the chemical conditions extending beyond the range of applicability of the ionic-activity correction method in the model.