Cellular automaton simulation of a simple corrosion mechanism: mesoscopic heterogeneity versus macroscopic homogeneity

A cellular automaton model that simulates the mesoscopic scale behavior of an electrode is presented in this article. Transition rules that mimic anod ic and cathodic events corresponding to a simple dissolution mechanism incl uding the presence of adsorbates and charge acceptor cations are introduced . The model focuses essentially on the case of a free corroding electrode, although polarized regimes are also examined. This mesoscopic approach disc loses features that are not considered in the standard macroscopic descript ion. First, the metal surface becomes morphologically heterogeneous. Second ly, the degree of roughness is linked to a specific distribution of active dissolution sites, and the resulting interplay between morphology and kinet ics carries with it a local segregation of reactants and the detachment of clusters of varying size. Issues concerning these distinguishing properties of the electrode surface are examined using morphogenetic descriptors. Mes oscopic balance equations are established and compared with the macroscopic standard equations for an homogeneous electrode. The influence of those pu rely mesoscopic features is addressed. We conclude that, although both the descriptions are different, they coexist consistently if a proper approach is chosen. (C) 2001 Elsevier Science Ltd. All rights reserved.