Alternating current (AC) impedance was used to evaluate the degradation of a high solids alkyd primer paint coating in a 3% NaCl solution, a 100% relative humidity (RH) environment after immersion in a 3% NaCl solution, and a 95% RH environment after immersion in a 3% NaCl solution. The results indicate AC impedance measures the amount of water absorbed into the coating through resistance results. A significant increase in capacitance may indicate a build up of corrosion products which causes blistering or debonding at the coating/metal interface, which may also be determined by diffusion tail analysis.