Can Finite Element Method Obtain SVET Current Densities Closer to True Localized Corrosion Rates?

Abstract

In this paper, the finite element method was used to simulate the response of the scanning vibrating electrode technique (SVET) across an iron–zinc cut-edge sample in order to provide a deeper understanding of the localized corrosion rates measured using SVET. It was found that, if the diffusion layer was neglected, the simulated current density using the Laplace equation fitted the experimental SVET current density perfectly. However, the electrolyte was not perturbed by a vibrating SVET probe in the field, so a diffusion layer existed. Therefore, the SVET current densities obtained from the local conductivity of the electrolyte would likely be more representative of the true corrosion rates than the SVET current densities obtained from the bulk conductivity. To help overcome this difference between natural conditions and those imposed by the SVET experiment, a local electrolyte corrected conductivity SVET (LECC-SVET) current density was introduced, which was obtained by replacing the bulk electrolyte conductivity measured experimentally by the local electrolyte conductivity simulated using the Nernst−Einstein equation. Although the LECC-SVET current density did not fit the experimental SVET current density as perfectly as that obtained from the Laplace equation, it likely represents current densities closer to the true, unperturbed corrosion conditions than the SVET data from the bulk conductivity.