A cellular automata model was used to study the diffusion characteristics in the corrosion film at a mesoscopic scale. The model focused on a metal/film/electrolyte system, including a series of local evolution rules. The effect of diffusion rate on the film growth and metal corrosion was investigated. The result showed that the growth rate of the film followed a power law with the diffusion steps, and the corrosion rate had the same law as that of the film growth in the model with the feedback effect. There existed a diffusing plane in the film, where the concentration of the diffusing species did not depend on time. The diffusion steps were found to have a great influence on the position and species concentration of the diffusing plane.
