Influence of synthesis temperature on electrochemical polymerization of o-anisidine on low carbon steel

Abstract

The influence of synthesis temperature on the electrochemical polymerization (ECP) of o-anisidine (OA) on low carbon steel (LCS) has been investigated. The ECP of OA was carried out on LCS substrate under galvanostatic conditions from aqueous solution of oxalic acid at various temperatures between 0 and 40 °C. The resulting poly( o-anisidine) (POA) coatings were characterized by potential–time ( E– t) curves, UV–VIS absorption spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The E– t curves reveal that the synthesis of POA coating at 0, 15 and 27 °C on LCS occurs in three stages, an induction time for ECP, passivation of LCS electrode surface via the formation of iron oxalate (FeC 2O 4·2H 2O) interphase and the dissolution of interphase and followed by ECP of OA. However, at 40 °C with an applied current density ∼0.66 mA/cm 2, the E– t curve shows the undesirable behavior which is attributed to non-decomposition of interphase during the third growth stage. As a consequence, at 40 °C the ECP of OA has not occurred on the LCS electrode surface. The XRD, SEM and optical absorption spectroscopy support this observation. It has been found that, as the synthesis temperature is increased, at low current densities, the induction time is observed to decrease, whereas it does not show any significant change at higher current densities. The optical absorption spectroscopy reveals the formation of mixed phase of emeraldine salt (ES) and pernigraniline base (PB) at 27 °C, whereas at lower temperatures the major portion of the coating constitutes the ES phase. The surface morphology, as revealed by SEM is observed to depend on the synthesis temperature.