Local impedance spectra of organic coatings

An atomic force microscopy (AFM) based approach to local impedance spectroscopy of organic coatings is presented. The impedance measurements were performed in a stationary regime with the AFM tip positioned on a surface of epoxy coated steel substrate. A set of voltage perturbation signals was applied between the tip and the substrate and impedance spectra were recorded in the frequency by frequency mode. The results were compared with the classical global impedance measurements and found to be consistent and complementary with those. They supplied additional information as far as identification and localization of coating defects is concerned.