AbstractElectrooxidation of aniline on conductive substrates, in an aqueous chloride electrolyte at low pH, produces adherent polyaniline (PANI) films. In the initial stage of polymerization the films exhibit a uniform globular microstructure which evolves to a fibrous deposit for thicker films. Although paraphenylenediamine (PPDA) itself does not electropolymerise to give a well defined electroactive film, in small admixtures it can modify dramatically the morphology of the copolymer with aniline. PPDA evidently promoted nucleation and cross‐linking during the electropolymerisation. Electrochemical characteristics and SEM micrographs of the doped PANI films are presented.