Computational simulation of metastable pitting of stainless steel

Metastable pit growth, a critical stage of pitting corrosion, has an important role in understanding pitting corrosion which involves a series of complicated interface electrochemical reactions. In this paper, a computational model which simulates metastable pit growth and its transition to stable growth is developed. The model based on the cellular automata approach contains several evolution rules that govern electrochemical reactions, solution reactions and diffusion. The results of simulated metastable pit growth kinetics are compared with the experiment data quoted from the literature. The influence of different factors including the diffusion of cations, the extent of the rupture of protective film, the pit radius and the existence of salt film on growth transition is analyzed. In order to improve the simulation efficiency, the Block algorithm is introduced which can accelerate the simulation of reaction-diffusion system. The mechanism of transition to passivity is discussed through comparing the simulation results with experimental data.