ONE-STEP ELECTROCHEMICAL PROCESS FOR THE FORMATION OF POLY(N-METHYLPYRROLE) COATINGS ON STEEL IN DIFFERENT MEDIA

Poly(N-methylpyrrole) coatings have been successfully formed on steel by a one-step electrochemical process in different media. Electropolym erization was performed in aqueous medium with low monomer concentrati on and in a mixed aqueous/organic media with higher monomer concentrat ions. Ethanol ( EtOH) and N,N-dimethylformamide ( DMF) were chosen as the organic components of the mixed solvents and oxalic acid was used as the electrolyte. The effect of process parameters on the formation of poly(N-methylpyrrole) was systematically investigated. The composit ion and morphology of the coatings were also studied by elemental anal ysis, FT-IR and scanning electron microscopy (SEM). Our results reveal that the formation and properties of poly (N-methylpyrrole) coatings were all dependent on the solvent composition and other process parame ters. The amount of poly(N-methylpyrrole) formed on steel increased wi th time and applied current for all the solvent-electrolyte systems. F or the electropolymerization performed in distilled water-oxalic acid solution, the amount of polymer coatings formed decreased with increas ed electrolyte concentration. In contrast, the amount of polymer coati ngs formed on steel in distilled water:ethanol (1:1)-oxalic acid and d istilled water:DMF (1:1)-oxalic acid systems, increased with increasin g electrolyte concentration. By controlling the electrochemical parame ters, smooth, uniform and strongly adherent coatings could be formed o nto steel substrates. (C) 1998 Elsevier Science S.A. All rights reserv ed.