Influence of acidic and alkaline environmental anticorrosive performance of epoxy coatings based on polyaniline/carbon nanotube hybrids modified with ionic liquid

Abstract

Polyaniline (PAni) and their hybrids with carbon nanotube (PAni@CNT) were prepared through inverse emulsion polymerization of aniline in the presence of different amounts of the ionic liquid (IL), 1-butyl-3-methyl-imidazolium tetrafluorborate (bmim.BF4). Transmission electron microscopy (TEM) was used to evaluate the morphology of the particles and cyclic voltammetry was employed to evaluate the electroactivity of these compounds in different pH media. The presence of IL promoted a great improvement of the redox activity of PAni@CNT in acidic medium and PAni in acidic and neutral media. Epoxy-based coatings containing 1 % of PAni and PAni@CNT were applied on carbon steel substrate to investigate their corrosion resistance using electrochemical impedance spectroscopy (EIS) technique. The coatings, deliberately scratched, were immersed in acidic and alkaline media. PAni@CNT hybrid presented better anti-corrosion response than PAni in acidic, neutral and alkaline environments and the presence of IL resulted in additional improvement of this property in all media. These results provide new possibilities for the preparation of environmentally friendly coating to be effective in a wide range of pH media. The morphology and band gap energy of the ER-based films were also investigated by optical micrograph and ultraviolet-visible spectroscopy, respectively. Narrower band gap energy was observed for the films containing hybrid materials mainly those containing IL in the hybrid, probably due to the improvement of charge transfer between particles promoted by the IL.