| Effects of metastable pits that have formed on an otherwise passive metal surface upon the nucleation of subsequent pits have been investigated by means of mathematical modeling and computer simulations. Various changes in local environment associated with a metastable pit are included in a spatiotemporal model to understand their role in triggering additional localized damage and in the formation of corrosion patterns on the passive metal surface. The local changes considered in the model include concentration, potential drop and oxide film damage. The properties of the model have been analyzed using mean-field approximations. Conditions that result in different regimes of metastable pitting activity, namely low activity, high activity and bistable behavior, have been identified.; Metastable pitting behavior has been simulated at a homogeneous surface for potentiostatic and galvanic coupling conditions and at a surface with inclusions for potentiostatic conditions. Simulations results show that the influence of metastable pits on future events becomes stronger with intensity of pitting. It has been shown that the interactions among metastable pitting events can lead to the formation of clusters of pits, thereby, causing deviations from the random behavior that is commonly assumed in the literature. In simulations with a homogeneous surface at potentiostatic conditions, clusters of pits grow with time to cover the entire surface under sufficiently aggressive conditions. Smaller clusters, on the other hand, are obtained under galvanic coupling conditions owing to the global inhibition effect of the potential drop.; Simulations with different spatial arrangement of inclusions at the surface have been carried out. The presence of inclusions enhanced metastable pitting activity even though a small fraction of the surface is covered with them. Intensity of pitting was higher with a cluster pattern of inclusions compared to randomly or regularly-distributed inclusions.; A fast removal of aggressive corrosion products from the surface reduced the intensity of metastable pitting in the simulations.; The last part of this dissertation presents experiments on bursting oscillations in the dissolution of iron in sulfuric acid. Bursting characteristics have been investigated as functions of the parameters external resistance, applied potential, acid concentration and electrode size. Both irregular and regular bursting oscillations have been found. |
