Anticorrosive performance of polyaniline/waterborne epoxy/poly(methylhydrosiloxane) composite coatings

In this paper, polyaniline (PANI) was used as anticorrosive filler and waterborne epoxy resin (EP) as film-forming material to prepare anticorrosive coatings on 304 stainless steel. Poly(methylhydrosiloxane) (PMHS) with low surface energy and divinylbenzene (DVB) as crosslinking agent were used to modify the coatings. FT-IR proved the successful preparation of Polyaniline and composite coatings. The micro-morphology and surface state of the coatings were studied by scanning electron microscopy (SEM) and contact angle measuring instrument (CA). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were used to evaluate the corrosion resistance of different coatings in 3.5 wt% NaCl solution. The surface of the composite coatings after surface modification became hydrophobic (CA = 98°), compact and uniform, and the anti-corrosion performance significantly improved. Compared with bare sheets, the |Z| 0.01Hz of the composite coatings had been increased by more than three orders of magnitude, and the corrosion current density had been reduced by five orders of magnitude. Long-term immersion test showed that the coating was able to provide effective protection to the substrate for about 140 days.