A Method for Determining the Corrosion Rate of a Metal under a Thin Electrolyte Film

Electrochemical impedance spectroscopy (EIS) was applied to evaluate corrosion rates of steels covered with a thin electrolyte film. A two-electrode cell consisting of a pair of identical steel plates embedded in epoxy resin was used for the EIS measurements under the thin electrolyte film. A transmission line type equivalent circuit was employed to describe the EIS behavior. Using this method, a charge transfer resistance was successfully estimated under uneven current distributions. This technique was applied to estimate the corrosion rates of steels under electrolyte film thickness in a range of 5 μm to 1 mm.