THE METAL-COATING ELECTROLYTE INTERFACIAL IMPEDANCE AND ITS GLOBAL FRACTAL MODEL

The impedance spectrum of an immersed coated metal specimen generally contains three frequency domains: the high frequency (HF) part represents the coating characteristic, the intermediate frequency (IF) part stands for the corrosion reaction and double layer behaviour, and the low frequency (LF) part is connected to the diffusion process. In general, each of these deviate from the ideal smooth interface model, because of the presence of some inhomogeneity, roughness, etc. In this paper, corrections to the ''ideal'' model are proposed supported by fractal insights. Moreover, the LF diffusional impedance is generalized towards a system of two serial diffusion layers, and the parts are assembled into an overall impedance model.