A model of ionic current densities in the vicinity of a corroding disk-shaped region

The scanning vibrating electrode technique (SVET) permits the measurement o f ionic corrosion current densities in a uniform electrolyte solution adjac ent to an anodic region in a corroding metal sheet. A credible model for su ch a corrosion experiment envisages a disk-shaped anode embedded in an infi nite coplanar sheet of more noble metal, serving as the cathode. If ohmic p olarization governs the corrosion rate, then Laplace's equation holds in th e steady state. Two independent, but different, solutions of this equation exist, both based on the premise that the two metallic regions have distinc t uniform electrical potentials. In this communication, we show these two s olutions to be equivalent and thereby predictions are made about the ionic current densities at points in solution near the corrosion site. These pred ictions are found to be qualitatively similar to reported experimental find ings. (C) 2001 Elsevier Science B.V. All rights reserved.