Improvement of the sacrificial behavior of zinc in scratches of zinc-rich polymer coatings by incorporating clay nanosheets

The aim of this study is to investigate the effect of clay nanosheets on the galvanic protection behavior of zinc in scribed areas of polymer zinc-rich coating. The scribed area is a simulation of damage in the coating in such a way that steel gets in contact with a corrosive solution and sacrificial behavior of zinc becomes important. Ultrasonic was applied to disperse nanosheets of clay in the epoxy resin. The clay content in the coating was varied from 0 to 3 wt.-%. The coatings were scratched for studying the galvanic behavior of zinc under damaged condition. Electrochemical impedance spectroscopy, open circuit potential measurements and surface techniques were chosen to investigate the corrosion protection performance of the coating and sacrificial properties of zinc. Transmission electron microscopy illustrated the separations of clay layers which interacted with epoxy resin. In addition, TEM images showed the dispersion of clay nanosheets between zinc particles in coating matrix. Open circuit potential (OCP) measurements showed that with increasing immersion time, the OCP shifted to the less negative potential values. The cathodic protection period and sacrificial properties improved in the presence of clay in coatings. Electrochemical impedance results indicated that addition of 1 wt.-% clay nanosheets enhances the corrosion protection performance of the epoxy zinc-rich coating without decreasing its sacrificial properties after long exposure times.