Adherent electroactive films of poly(o-phenylenediamine) (PPD) were obtained by electropolymerization of o-phenylenediamine (o-PD) on 304 stainless steel under potentiostatic conditions. The iri situ Fourier transform infrared reflectance spectroscopy study suggests a phenazine ring ladder-structure polymer. Open circuit potential and potentiodynamic studies of PPD-coated steel electrodes, in chloride aqueous solution show a positive shift of the corrosion potential.