Determination of resistivity profiles in anti-corrosion coatings fromconstant-phase-element parameters

A recently proposed model which explains the CPE response exhibited by metal/coating/electrolyte systems as the result of power-law dependences of the coating resistivity and permittivity along their thickness is revisited and applied to three different coating/electrolyte combinations. It is shown that resistivity profiles may be determined, and their evolution with the time of exposure may be followed. The effect of the assumptions made on coating and electrolyte resistivity on the regressed parameters is discussed and the factors which affect the reliability of the measured water uptake are highlighted. It is shown that both the composition of the coating and that of the test solutions influence the time dependence of the coating performance.