Enhancement of photooxidative and corrosion resistance of epoxy/graphene water-based coatings on metallic substrate

Graphene nanoplatelets (GNPs) dispersed in low quantity in a waterborne epoxy resin enhance the coating anticorrosive properties and strongly contrast its photooxidative degradation. The study of the photooxidative behaviour monitored until 600 h, highlights a very relevant result from an applicative point of view. A low percentage of GNPs (1% by weight) determines a reduction in the increase of the carbonyl groups amount of 78 wt% compared to the unfilled sample. Furthermore, a low quantity of GNPs incorporated in the organic coating reveals a significant enhancement in the corrosion resistance, as demonstrated by electrochemical analysis. Results show that the greater the amount of GNPs the slower the absorption. Equivalent electrical circuits, by means of the "two-parallel-layer" model, are used to interpret the electrochemical behaviour, considering the complex nature of the waterborne and inhibitors free coating. A new promising strategy is foreseen for enhancing the performance of the coating service life.