Electrochemical impedance spectra were measured for the aluminum electrodes coated and uncoated with an epoxy cresol novolac film in 0.5mol·dm^-^3 NaCl solution (60℃) at open circuit petential, respectively. By fitting the Nyquist curves thus obtained with the equivalent circuit generally used for coated electrode, the values of the film resistance, the film capacitance, the electrochemical reaction resistance and the double layer capacitance at metal/coating interface obtained were used to estimate the mechanism of the penetration of water into the film which is demonstrated to be conducted by chemical channels. After the film has been in the said solution for 8h, its dielectric constant is 5.2 calculated from the film capacitance, which is found to be close to that of the dry film determined using a Q meter.

Key words: EPOXY RESINS, COAT