Corrosion protection of carbon steel and copper by polyaniline and poly(ortho-methoxyaniline) films in sodium chloride medium. Electrochemical and morphological study

The aim of this work was to obtain polyaniline (Pani) and poly(ortho-methoxyaniline) (Poma) by chemical synthesis and to evaluate their corrosion protection properties on carbon steel (CS) and copper (Cu) in an aggressive media such as sodium chloride. The syntheses of the polymers were carried out by chemical oxidation of the monomers by (NH₄) ₂S₂O₈ in nitric acid solutions. Under these conditions, the polymers were obtained in the oxidized form, dissolved in 1-methyl-2-pyrrolidone and casted by solvent evaporation onto the metallic substrates (carbon steel and copper) for corrosion evaluation. The morphology of the polymers was evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The electrochemical behavior was determined by open circuit potential (OCP) measurements and polarization curves (PC). The best results were obtained with Pani because this polymer film participates in the formation of an oxide film at the polymer-metal interface, a phenomenon which is not observed with Poma. This oxide film increases the barrier effect that the polymeric film has by itself.