Abstract
Transport-limited dissolution of metals in corrosion pits is associated with the product of the metal ion diffusion coefficient and total concentration of metal ions (DM+路Ctot). In one dimensional (1D) pit dissolu-tion, the concentration of ionic species varies with location in the pit; at the dissolving pit bottom, the saturation of metal ion and supporting anion is ex-pected under transport control conditions, while the metal ion is nearly depleted at the pit mouth. To describe metal ion transport through pit solution with constantly-changing concentration, an effective diffusion coefficient (Deff) is proposed in this study with consideration of the combined effects of vis-cosity, temperature and electric field inside a grow-ing 1D pit. The modeled Deff路Ctot values were calcu-lated and compared with experimental DM+路Ctot val-ues for S13Cr 1D pit dissolution in different bulk chloride concentrations at 85掳C. The modeled Deff路Ctot values were very close to the experimental values, validating the modeling approach suggested in this study.
