Analysis on organic film degradation by dynamic impedance measurements

Degradation of the organic coating film on the carbon steel has been investigated by dynamic impedance measurements. Since the permeation of water into the coating progresses in short period after the immersion, the time-stability of the electrode system is not satisfied while measuring the electrochemical impedance. As the result, the impedance spectrum in the low frequency region is distorted with the electrode that does not satisfy the time-stability. In the present paper, a dynamic impedance spectroscopy is applied to the electrode without the time-stability, and the distortion of impedance spectrum in the low frequency region is compensated. The degradation process of the coated metal was analyzed by the curve-fitting of the compensated impedance spectra with the equivalent circuit.