ELECTROSYNTHESIS OF ADHERENT POLYANILINE FILMS ON IRON AND MILD-STEELIN AQUEOUS OXALIC-ACID MEDIUM

Polyaniline (PANi) films can be electrosynthesized by oxidation of ani line on iron and mild steel in a one-step process from an aqueous oxal ic acid medium which passivates substrates. Homogeneous and strongly a dherent films of controlled thickness can be deposited either in the p otentiodynamic or galvanostatic modes. These films are characterized b y IR, X-ray photoelectron spectroscopy (XPS), gel permeation chromatog raphy (GPC) and matrix-assisted UV-laser desorption ionization (MALDI) techniques, and have a structure similar to that of PANi deposited on platinum. Iron samples coated with PANi exhibit much better protectio n against corrosion in an acidic solution (0.4 M NaCl + 0.1 M HCl) tha n the polypyrrole-coated ones. Attempts to grow PANi films on zinc or zinc-nickel alloy in oxalic acid were unsuccessful because the formati on of insulating layers prevents electropolymerization. (C) 1998 Elsev ier Science S.A. All rights reserved.