Smart epoxy coating modified with isophorone diisocyanate microcapsules and cerium organophosphate for multilevel corrosion protection of carbon steel

Abstract

This study investigates the corrosion resistance of steel plates coated with epoxy-based coatings modified with microcapsules loaded with isophorone diisocyanate and with pH-sensitive cerium tri(bis(2-ethylhexyl)phosphate (Ce(DEHP)3) particles serving as inhibitor. The healing effects were studied by combining different localized electrochemical techniques, namely localized impedance spectroscopy (LEIS), localized potentiometry (SIET) and the scanning vibrating electrode technique (SVET). The impact of the additives in the coating barrier properties was assessed by electrochemical impedance spectroscopy (EIS). EIS evidences a relevant multilevel protection effect when both additives are combined, effect that is characterized by higher and more stable coating barrier properties and absence of interfacial corrosion activity. The corrosion healing ability over defects formed in the coating formulated with the combination of the two additives was confirmed by LEIS. SVET and SIET also evidence that the overall healing process in the coating modified with both additives involves the combination of the protective role of each individual species, that reinforces significantly the corrosion protection conferred by the epoxy coating.