The Electrical Properties of Protective Polymer Coatings as Related to Corrosion of the Substrate

Abstract

The effective electrical permittivity of polymer‐coated steel was measured between 200 Hz and 100 kHz as a function of time of exposure to . The real and imaginary parts of the permittivity increased over the entire frequency range as a consequence of electrolyte penetration. The development of a −1 slope on the log loss vs. log frequency curve suggested localized penetration of the dielectric coating by a conducting phase. This behavior correlated with the onset of visible localized corrosion. Results were discussed in terms of a metal/metal oxide/penetrated‐coating model.