Numerical Simulation of Crevice Corrosion

Abstract The process of crevice corrosion consists of anodic metal dissolution from the alloy to the crevice solution, cathodic reduction of oxygen on the bold surface of the metal outside the crevice, metal ion hydrolysis reactions, and mass transfer between the crevice solution and the bulk solution. The mass transfer process mechanisms are ionic migration and diffusion. An improved mathematical model has been developed for the numerical simulation of the incubation period of crevice corrosion. The model utilizes a new equation for the transport processes, which includes both ionic migration and diffusion. An explicit finite-difference technique is applied to a uni-dimensional crevice along the crevice depth, with appropriate boundary conditions at both the crevice tip and bulk solution. Use of the surface profile of the crevice in the modelling of the ionic migration and diffusion processes leads to a much more accurate simulation of the crevice corrosion process. Narrow crevices within the overall crevice can achieve active corrosion, while the rest of the crevice remains completely passive, whether these narrow crevices are found at the tip, middle or mouth of the crevice. Therefore, active corrosion can occur for any crevice having a crevice depth that is greater than the depth required for deoxygenation, depending on the crevice gap profile.