Interaction of interfacial debonding and under-film corrosion propagation at the edge of the blistering area of epoxy coating

Abstract

The blistering of epoxy coating and its evolution were investigated after exposure to 3.5wt.% NaCl solution. The evolution of under-film corrosion could be divided into four stages, according to the observation of the corrosion morphology and the distribution of corrosion products and elements. Corrosion propagation was related to the distribution of media at the edge of the blistering area. Analysis of local electrochemical impedance spectroscopy revealed that local impedance mapping could help to predict the direction of corrosion propagation. It was proposed that the interfacial debonding at the edge of the blistering area was a necessary condition for corrosion propagation.

Keywords: Epoxy coating; LEIS; blistering; under-film corrosion; interfacial debonding