Comparison of polyaniline electrodeposition on carbon steel from oxalic acid and salicylate medium

• Influence of electrolyte medium on the nature of polyaniline coating.
• Importance of passivation prior to the electropolymerization on active metal substrates.
• Method to form transparent polyaniline coatings on active metal surfaces.

Polyaniline (PANI) coatings on carbon steel (CS) substrate were electrodeposited from two different mediums such as oxalic acid (H2C2O4) and sodium salicylate (C7H5NaO3). In oxalic acid, the importance of the passivation of the carbon steel surface prior to PANI electrodeposition was investigated by linear potentiodynamic test. It showed below 0.3 M oxalic acid concentration PANI film formation was not complete. The extent of passivation of the carbon steel was found to depend on the strength of the oxalic acid, which determined the formation and the nature of the PANI film. Whereas, deposition from the sodium salicylate solution did not show any passivation peak, but resulted in the formation of a transparent, uniform, compact and adherent PANI coating. The formation, morphology and characteristics of the coatings were compared by cyclic voltammetry, scanning electron microscopy (SEM) and Raman spectroscopy.