Aniline pentamer-modified reduced graphene oxide/epoxy composites as anticorrosion coatings

A series of composite coatings that consist of electroactive epoxy thermoset (EET) containing pendant aniline pentamer and reduced graphene oxide (rGO) platelets was prepared, characterised and applied as anticorrosion coatings. Diamine monomer with pendant unilateral amino-capped aniline pentamer (DAAP) was prepared by reacting the as-prepared aniline pentamer (AP) with 2,6-difluorobenzoyl chloride then reacted with 4-aminophenol. The chemical structure of AP, and DAAP was characterised by FTIR, NMR and mass spectroscopy. The EET composite coatings were prepared by reacting DAAP with epoxy resin in the presence of suitable feeding ratio of GO/rGO at specific programmed heating and then characterised by TEM. The corrosion protection of cold-rolled steel electrode coated with Non-EET (NEET), EET, GOEET and rGOEET was investigated by performing a series of electrochemical corrosion measurements (such as Tafel, Nyquist and Bode plots) in saline condition. Notably, the corrosion protection of coatings revealed the following trend: rGOEET＞GOEET ＞ EET ＞ NEET over a short- and long-term anticorrosion performance. The best anticorrosion performance of rGOEET composite coatings resulted from the synergistic effect of the excellent O2 barrier property, caused by the efficient dispersion of rGO in the EET matrix, and the formation of passive metal oxide layers induced by the pendant AP existing in EET coating. Moreover, the proposed composite showed excellent mechanical properties. This method of pendant aniline pentamer cold open the door for further investigations of other pendant electroactive polymers towards efficient coating materials.