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. Electropolymerization was performed in aqueous medium with low monomer concentration and in a mixed aqueous/organic media with higher monomer concentrations. 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 composition and morphology of the coatings were also studied by elemental analysis, 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 parameters. The amount of poly(N-methylpyrrole) formed on steel increased with time and applied current for all the solvent-electrolyte systems. For the electropolymerization performed in distilled water-oxalic acid solution, the amount of polymer coatings formed decreased with increased electrolyte concentration. In contrast, the amount of polymer coatings formed on steel in distilled water:ethanol (1:1)-oxalic acid and distilled water:DMF (1:1)-oxalic acid systems, increased with increasing electrolyte concentration. By controlling the electrochemical parameters, smooth, uniform and strongly adherent coatings could be formed onto steel substrates.