Electrochemical synthesis and anticorrosive properties of Nafion®–poly(aniline-co-o-aminophenol) coatings on stainless steel

The objective of this work was to compare the electrochemical behavior and possible anticorrosive properties of composite with Nafion®, poly(aniline-co-o-aminophenol) (P(An-co-OAP)) and polyaniline (PAn) films with those of corresponding simple films. The electrochemical synthesis of polymer films was carried out on stainless steel AISI 304 (SS) surfaces by using the cyclic potential sweep (CPS) deposition. Scanning electron microscopy (SEM) was used for the characterization of the structure and morphology of deposited films. Evaluation of anticorrosive properties of films in 0.5 M H2SO4 without and with chlorides was achieved by monitoring the open circuit potential (EOC) of coated SS electrodes as well as by tracing the anodic current–potential polarization curves. These studies have shown that the SS remains in its passive state in the presence of polymer coatings. Composite with Nafion®, P(An-co-OAP) and PAn films, keep their redox activity in chloride-containing acid solutions providing almost a complete protection of the SS substrate against pitting corrosion. These films prevent chloride exchange with solution because of the cation permselectivity of the Nafion® membrane. The charge compensation during redox reactions occurs mainly by protons since sulfonate groups of Nafion® act as dopants in composite films. The redox behavior of the Nafion®–P(An-co-OAP) film is improved as compared with that of the Nafion®–PAn film in both Cl−-free and Cl−-containing solutions. This behavior may be ascribed to the functional group –OH that facilitates charge compensation through proton during redox reactions.