Evaluation of organic oatings with electrochemical impedance spectroscopy. Part 2: Application of EIS to coatings

EIS can generate quantitative data that relates to the quality of a coating on a metal substrate. EIS is a very sensitive detector of the condition of a coated metal, so the EIS response can indicate changes in the coating long before any visible damage occurs. EIS is not an absolute measurement. An EIS spectrum only tells us something when we compare it to another EIS spectrum. Any experiment designed to measure coating quality must include a mechanism to stress the coating and induce its failure. By making periodic EIS measurements during the stress process, a rate of coating failure can be estimated. EIS is a nondestructive measurement, so we can use EIS to track the condition of a coated metal sample as it changes. In most cases, it is possible to identify the cause of coating failure.