Cellular automaton simulations of corrosion pit growth

The evolution of corrosion pit growth on the surface of a metal in an aggressive medium is investigated with a simple cellular automaton model defined at a mesoscopic scale. A diffusion control of the electrolyte species is assumed, and for the elementary physicochemical process, such as mass transport, metal dissolution and passivation, some simple interaction rules are proposed and analyzed in regarding with the electrolyte concentration, dissolution probability and passivation probability. We assume that the number of dissolved metal sites represents the dissolution current, and the pit depth is represented by the number of dissolved metal sites at the longitudinal on the two-dimensional square lattice. For the different dissolution probability and passivation probability, the laws of the dissolution current with time are investigated, which obey the time power function. Therewith the curve of pit depth for different time is obtained.