Organic coatings are widely used in the steel structures of power transmission and distribution
systems to protect against corrosion. Early and accurate detection of coating degradation is
clearly of critical importance. We investigated two methods for evaluating coating
degradation—the alternating current (AC) impedance method and the current-interrupt (CI)
method—by exposing coated steel specimens to either long-term atmospheric exposure or
shorter-term salt-water immersion, and then measuring their electrochemical behavior. We
also analyzed coating degradation by x-ray probe microanalysis.
Key words: Coating, Corrosion, Electrochemical techniques, Alternating current impedance,
Current interrupt method, Under-film corrosion