Sensing electrochemical activity in polymer-coated metals during the early stages of coating degradation by means of the scanning vibrating electrode technique

Application of scanning vibrating electrode technique (SVET) for corrosion studies of organic coatings on reactive metals is presented. SVET was used to monitor the electrochemical processes at painted steel immersed in either 10 mM Na2SO4 or 10 mM NaCl aqueous solutions. The coated samples were investigated after a scratch was operated through the polymer matrix down to the metal–substrate surface in order to simulate a defect across the coating. SVET imaging probes that the electrochemical behaviour of the system is different depending on the electrolyte employed. Enhanced coating delamination originating from the defect is observed when chloride ions are present in the environment.

Research highlights
► Electrochemical behaviour in the scratch is different depending on the electrolyte.
► Cathodic sites distributed below the coating are detected with SVET.
► Enhanced coating delamination originates from the defect when chloride is present.