USING ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY AS A TOOL FOR ORGANIC COATING SOLUTE SATURATION MONITORING

Electrochemical impedance spectroscopy (EIS) has been used to study the solute uptake for epoxy/phenolic (E/p) and epoxy/amine (E/a) thick-coated mild steel samples immersed for 160 days in 3.5 weight percent NaCl solution exposed to air. Samples with thicknesses of approximately 200 mum with an exposed surface area of 22.6 cm2 were used to follow solute saturation of the organic coating. Good agreement was obtained between the calculated and measured coating capacitance when, according to the diffusion equation, the coating capacitance was plotted against exposure time.