A model for an anodic dissolution cell in connection to its dimensions for stress corrosion cracking

The anodic dissolution is modelled for pure iron for conditions simulating those of low alloy steels in high temperature water undergoing stress corrosion cracking. The dissolution is assumed to be initiated by the rupture of the protective oxide film and arrested by the repassivation. The goal of the model is to identify the relevant parameters of the anodic dissolution by a parameter sensitivity study. The cell is three-dimensional for taking into account the cathode to anode area ratio, at the price of the assumption of homogeneity of the electrolyte, and is assumed to be electrically uncoupled from the rest of the crack. The model uses the Butler-Volmer, the Ohm law, the charge conservation, and takes into account the passive current. The main results include the limited extent of the cell along the crack, depending on the values of the parameters, and non-linear and coupled effects for the occurrence and amplitude of the dissolution with as critical parameters the composition of the electrolyte, the exchange current densities and the anode dimensions.