Electrochemical polymerization of 2,5-dimethylaniline on low carbon steel

Abstract

The electrochemical polymerization (ECP) of (2,5-dimethylaniline) (DMLA) in an aqueous solution of oxalic acid on low carbon steel (LCS) under galvanostatic conditions has been investigated. The resulting PDMLA coatings were characterized by potential–time ( E– t) curves, X-ray diffraction (XRD) measurements, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and UV-Vis absorption spectroscopy. It has been found that the oxalic acid is a suitable medium for the ECP of DMLA on the LCS substrate and the electrochemical growth process is characterized by three distinct stages: (i) dissolution of the LCS electrode surface and formation of polycrystalline iron oxalate (FeC 2O 4·2H 2O) interphase, (ii) complete passivation of LCS electrode surface and (iii) decomposition of the interphase followed by the ECP of DMLA. The induction time is found to decrease with the increase in the applied current density. The optical absorption spectroscopy study revels the formation of the mixed phase of pernigraniline base (PB) and emeraldine salt (ES) form of PDMLA at higher current densities (>0.66 mA/cm 2), whereas at low current density (∼0.66 mA/cm 2) the major portion of the coating constitutes the PB form. The surface morphology of PDMLA coating is observed to depend on the applied current density and it improves with the increase in the current density.