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

摘要

A cellular automaton model that simulates the mesoscopic scale behavior of an electrode is presented in this article. Transition rules that mimic anodic and cathodic events corresponding to a simple dissolution mechanism including 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 discloses features that are not considered in the standard macroscopic description. First, the metal surface becomes morphologically heterogeneous. Secondly, the degree of roughness is linked to a specific distribution of active dissolution sites, and the resulting interplay between morphology and kinetics 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. Mesoscopic balance equations are established and compared with the macroscopic standard equations for an homogeneous electrode. The influence of those purely mesoscopic features is addressed. We conclude that, although both the descriptions are different, they coexist consistently if a proper approach is chosen.