Further modeling of chloride concentration and temperature effects on 1D pit growth

The product of diffusion coefficient and saturation concentration of metal ions (D_M+·C_tot) is associated with steady state dissolution of metal in corrosion pits. In our previous paper, D_M+·C_tot was modeled for one dimensional (1D) pit dissolution of super 13Cr stainless steel (S13Cr) by taking into account the common ion effect, as well as viscosity and temperature influences. However, the modeled values were only half of the experimentally-measured D_M+·C_tot, implying that D_M+ and/or C_tot were underestimated. To improve the modeling of D_M+·C_tot, the effects of complexation and electromigration were additionally considered, which led to the definition of effective diffusion coefficient (D_eff) applicable for the diffusion of metal ionic species under the combined effect of viscosity, temperature and electric field inside a growing 1D pit. The newly modeled D_eff·C_tot values were very close to the experimental values, validating the modeling approach described in this paper.