Numerical simulations of spatial heterogeneity formation in metal Corrosion

We use a cellular automata model to describe an example of pitting corrosion process. The process is initiated by a local damage of the protective layer covering the material. For several properties we observe a transition between two regimes. A stationary regime is followed by a diffusion limited regime. A separation of acidic and basic zones is observed in the solution. These zones are, respectively associated with smooth and rough part on the internal pit surface. We show that the disposition of theses zones is a stochastic event that governs the morphology of the pit. This later grows as a smooth hemispheric surface at the early stage of the process and switches to a more complex morphology in the diffusion limited regime. The mechanisms behind this roughening transition are analyzed.