TRANSPORT AND REACTION DURING PITTING CORROSION OF NI IN 0.5M NACL

A finite-element model was developed to simulate potential dependent dissolution of a two-dimensional cylindrical trench in the presence of fluid flow. The model includes multiple species in solution, reaction equilibria, and transport by convection, diffusion, and migration. Simulations were performed for parameter values that correspond to the pitting of nickel in 0.5M NaCl. It was found theoretically that, for this system, fluid flow would cause a decrease in the dissolution rate owing to potential-field effects. Also, rinsing of the cavity was predicted for high flow rates. Experimental observations were in agreement with the theoretical predictions, even though the geometry of the two systems was distinctly different. Repassivation of corrosion pits was observed experimentally at flow rates for which the dimensionless Peclet number exceeded 10(3).