Electrochemical impedance spectroscopy is used as a nondestructive method for investigating the electrochemical properties of carbon/nylon 6 composites exposed to aqueous 3.5 weight percent NaCl at ambient and high hydrostatic pressure. Electrochemical impedance spectroscopy is a sensitive technique that can distinguish between basal and edge crystallographic orientations of bare carbon fibers and can distinguish between a poorly consolidated composite and a properly consolidated composite. Electrochemical characteristics of the carbon/nylon 6 composite are followed by monitoring changes in the impedance spectra caused by exposure to high hydrostatic pressure or by electrochemically induced damage. An equivalent circuit model is proposed herein that gives a good fit to experimental data, where the high frequency response is due to the behavior of the nylon matrix and the low frequency response is due to the existence of an infinite length Warburg diffusional impedance associated with the carbon/electrolyte interphase.