Preparation And Characterization Of The Polyaniline Anti-corrosion Coating

Because of its excellent physical properties including ductility, electrical conductivity and thermal conductivity, metals are fundamental materials in the industry and daily life. But,corrosion process will deteriorate the metal structure’s performance, which bring huge financial losses and disaster results. In order to protect the metal from corrosion, protective films, also called anti-corrosion coatings, are usually applied on the surface of the substrate. Epoxy resin is one of the most widely used resins used for anti-corrosion coating. In the film forming process, toughening agent is usually added into the coat in order to promote the coating’s toughness because the curing product of the epoxy resin is of high brittleness. Polyamides,the curing agent,are mostly used to improve the tenacity of epoxy coating and their curing product has outstanding adhesion property and shielding performance. But epoxy/ polyamide coating alone can’t meet the requirements of the higher demand for the anti-corrosion performance. Polyaniline, one of the eco-friendly conducting polymers and can facilitate the formation of compact passive films, widely used to promote the anti-corrosion performance of the coatings. Nevertheless, the dispensability of polyaniline in the coating is poor because of its insolubility and infusibility,putting a limit on the development of polyaniline/epoxy anti-corrosive coating.In this work, epoxy/polyamide coatings using Epoxy-E51 as binder and different amount of polyamide-651 as curing agent were fabricated at room temperature. The performance of the coatings were characterized by immersing the samples in the 12% NaCl solution at 95℃ and the relationship among anti-corrosion performance 、 adhesion performance and immersion time was tested. The experimental results indicated that the coating prepared by mass ratio of epoxy resin-E51 to polyamide-651 at 100:35 had the best performanceIn order to improve the coating’s protective performance, polyaniline was added into the coating. Coatings containing PANI with mass fraction at 0.5%, 1%, 1.5% and 2% were prepared, respectively. The experimental results indicated that coating with 1.5% polyaniline had the best anti-corrosion performance.With the purpose of analyzing the particle size effect of polyaniline on the anti-corrosion performance, the bigger particles of polyaniline were removed from the dopes. After removing the particles of poor dispersion through centrifugation, the anti-corrosion performance of original 0.5%PANI coating, 1.0%PANI coating and 1.5%PANI coating were weakened, while the anti-corrosion performance of original 2% PANI coating was improved. Analysis results showed that:When the polyaniline content in the coating is no higher than 1.5%, the particles of poor dispersion had a simulative effect on the anticorrosion performance; otherwise, when the polyaniline content in the coating increased to 2%, the particles of poor dispersion would greatly weaken the corrosion protection performance.