Degradation of protective organic coatings after cupping test

Coil coating products generally are shaped by deforming and bending after coating. These deformations can produce defects inducing a significant deterioration of the protective properties of the organic coating. An empirical method for the evaluation of the deformation effects is the cupping test. In the present work, effects of the cupping test were studied by using electrochemical impedance spectroscopy (EIS) measurements to study the influence of deformation conditions on the mechanisms of degradation of the protective properties. The materials studied were environmentally friendly coatings based on ion exchange pigments. In addition to the electrochemical characterizations, a finite element model was developed for the estimation of the strain after the cupping test and some adhesion measurements were performed. The cupping test with an electrochemical characterization with EIS is a valid method for the evaluation of the protective behavior of coil coating products after deformation. © 1999, NACE International.