IR and XPS studies on the interphase and poly(N-methylpyrrole) coatings electrodeposited on steel substrates

Poly(N-methylpyrrole) coatings have been electrodeposited on steel substrat es from aqueous oxalate solutions. The formation process of the coatings wa s found to be different between acidic and basic mediums. In an acidic medi um, the reactions were characterized by two stages: formation of the passiv e interphase and electropolymerization of the N-methylpyrrole. The composit ion of the formed interphase and poly(N-methylpyrrole) coatings were examin ed by infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) . Our results show that the interphase formed in an acidic medium is compos ed of iron(II) oxalate dihydrate. The formation of poly(N-methylpyrrole) co atings on steel occurred after the passivation of steel was completed. Inte raction between the poly(N-methyl pyrrole) coatings and the interphase is s hown by the broadening of the -CO absorption peak. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.