Growth of poly(2,5-dimethoxyaniline) coatings on low carbon steel

Poly(2,5-dimethoxyaniline) (PDMA) coatings on low carbon steel (LCS) substrates have been grown by the electrochemical polymerization (ECP) of 2,5-dimethoxyaniline (DMA). The ECP was carried out in an aqueous solution of oxalic acid at room temperature under galvanostatic conditions. Uniform, strongly adherent dark green PDMA coatings were obtained on LCS substrates. These coatings were characterized by potential-time (E-t) curves, UV-visible absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). It has been found that the oxalic acid is a suitable medium for the ECP of DMA on the LCS substrate and the electrochemical growth process is characterized by three distinct stages-induction time for ECP of DMA, complete passivation of LCS electrode surface and decomposition of the interphase followed by the ECP of DMA. The induction time is observed to decrease with increase in the applied current density. The optical absorption spectroscopy study reveals the exclusive formation of emeraldine salt (ES) phase of PDMA at lower current density whereas at higher current density coating constitutes the mixed phase of emeraldine base (EB) and ES. The FTIR spectroscopy indicates that the formation of PDMA coating. The surface morphology of PDMA coating is observed to depend on the applied current density and it improves with the increase in the current density. (C) 2003 Elsevier Science B.V. All rights reserved.