Electrochemical impedance spectroscopy; A tool for organic coatings optimizations

Electrochemical impedance spectroscopy (EIS) was applied to the optimization of automotive electrodeposited coatings, container interior coatings and industrial maintenance coatings. The electrochemical impedance data were used to predict corrosion protection, film porosity, solution absorption into the coatings and film delamination properties. Variables such as resin contents, crosslink densities, cure temperatures, and solvent types and contents were evaluated for these various types of coatings. In general the electrochemical impedance data correlated well with conventional exposure tests results such as salt fog, cyclic scab corrosion and delamination tests. The impedance spectra permits a rather rapid (15-75 min per sample) assessment of the film's characteristics even when no visually observable changes have occurred. Electrochemical impedance spectroscopy provides a technique to optimize coatings'-while reducing the time of coating evaluations and gives insight into the chemical and physical properties of the coatings.