Application of impedance imaging to evaluation of organic coating degradation at a local scale

A new approach for evaluating the local electrical properties of organic coatings has been proposed. It was performed with contact mode atomic force microscopy (AFM). A current response signal was measured when a single-frequency voltage perturbation was applied between AFM tip and coated metal. Suitability of the proposed technique has been presented on the representative acrylic coating degraded by two different factors—UV radiation and electrolyte exposure. It was possible to disclose the early stages of the coating deterioration, to spatially localize defective regions, and to observe distinctly different modes of the coating degradation as a result of exposure to various degradation factors.