Electrodeposition of ring-substituted polyanilines on Fe surfaces from aqueous oxalic acid solutions and corrosion protection of Fe

The electrochemical polymerization of several ring-substituted anilines nam ely of o-toluidine (o-Tol), m-toluidine (m-Tol), o-anisidine (o-Anis) and o -chloroaniline (o-ClAn) was carried out on passivated Fe surfaces. Thin pol ymeric films were deposited by cyclic voltammetry, potentiostatic or galvan ostatic techniques on the Fe-disc electrode from aqueous oxalic acid soluti ons. Well-defined cyclic voltammograms showing the electroactivity and grow th of polymers were observed during each potential cycle. The electrochemic al response and the surface morphology of the deposited polymeric films of substituted polyanilines were characterized in comparison with the non-subs tituted polyaniline films on Fe. Adherent and relatively stable polymeric f ilms were obtained for o-Tol, m-Tol and o-Anis. These films show protective properties against corrosion of Fe in sulfuric acid solutions stabilizing the Fe passive state. Their anti-corrosion behavior, although slightly poor er than that of the non-substituted polyaniline, bears strong similarities with that of the polyaniline. A less conductive polymer with a very poor st ability and protective ability against the corrosion of Fe was obtained for o-ClAn. (C) 2001 Elsevier Science B.V. All rights reserved.