Dielectric Properties Reflecting Coating Performance

The use of electrochemical impedance spectroscopy (EIS) in coatings research is widespread. The information obtained by this technique is often limited, which is the result of too-high expectations and inadequate analysis and interpretation. Analysis of the dielectric properties of organic coatings using a constant phase element in the equivalent circuit reveals detailed information on coating properties at curing stage, water uptake and electrolyte sensitivity, swelling, and onset of delamination, and also on the weathering of the coating. The determination of weathering using EIS is developed further, and a quantitative parameter the Weathering Index is introduced. Examples of results on coatings exposed to several types of accelerated weathering are given. (Author)