Examination of organic coatings on metallic substrates by scanning electrochemical microscopy in feedback mode: revealing the early stages of coating breakdown in corrosive environments

Abstract

Scanning electrochemical microscopy in feedback mode was used to monitor changes in the surface state of a polymeric film applied on a metallic substrate when exposed to an aqueous electrolytic environment. The protected metal consisted of a carbon steel substrate coated with a polyurethane-based polymeric film. SECM measurements performed in the presence and absence of chloride anions permitted a specific effect caused by Cl- anions at early exposures to be detected. Significant surface roughening is observed for immersion times shorter than one day when the electrolyte contains chloride ions. Additionally, the growth of an individual blister could also be investigated