Modeling Crevice Corrosion of Pure Chromium by Coupling of Phase and Polarization Behavior

Abstract In a recent paper, a crevice corrosion model for pure chromium was presented aiming at basic understanding of the local corrosion mechanism in an already deoxygenated crevice with a given geometry. The time stepwise calculation of chromium dissolution was based on arbitrarily selected levels of initial corrosion potential and slopes of the cathodic polarization curve at the open surface in contact with the bulk liquid. As a basic feature, the anodic polarization slopes inside the crevice were controlled by the mass of the precipitated chromium hydroxide phase, which was thermodynamically calculated from the resulting crevice solution composition using the tentative quaternary phase diagram: water—chromium—chromium hydroxide—chromium chloride. The present paper applies additional oxygen diffusion calculation steps and demonstrates the effects of various crevice widths, chloride contents, and bulk oxygen contents diffusing into the crevices at pH = 6. The calculations are based on the assumption of...