Corrosion protection of carbon steel with thermoplastic coatings and alkyd resins containing polyaniline as conductive polymer

Protection against corrosion was evaluated for specimens of carbon steel coated with conventional thermoplastic polymers as a blend of poly(methyl methacrylate) with poly(butylmethacrlylate), phenoxy resin and a poly(vinyl chloride-co-vinyl acetate) 90/10 copolymer and compared with an alkyd resin containing 0.2, 0.4 and 0.6% (w/w) of polyaniline, a conductive polymer extensively investigated for its ability to protect metals against aqueous corrosion. Previously, physicochemical and thermal characterization of the polymers was carried out and specimens of carbon steel were used in order to evaluate the protective power of these coatings. Field tests in urban and marine environments were compared with laboratory accelerated tests. Coatings degradation and corrosion products were related to the different mechanism of corrosion processes that take place in thermoplastic and alkyd resins. Equivalent time of laboratory tests with respect to field tests was also evaluated in order to validate the accelerated cyclic tests. In both cases, field and laboratory conditions, the presence of conductive polymer in alkyd resin improve the protection against corrosion of the metal and the degradation resistance of the coating, improving the overall performance of the coated steel.