Electrochemical behavior of steel/acid interface: adsorption and inhibition effect of oligomeric aniline

The present work shows the development of new protective oligomeric aniline (O-ANI) and its effect on electrochemical corrosion behavior of low carbon steel (LCS) in 1 M HCl at 308 K. The synthesized O-ANI was subjected to spectroscopic and electrochemical characterizations. The inhibition of LCS corrosion by O-ANI was studied using open circuit potential (OCP), potentiodynamic polarization (PDP), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements. The potentiodynamic polarization data indicated that O-ANI suppresses predominantly the cathodic process of corrosion reaction in comparison to the anodic process. The inhibition efficiency of the O-ANI depends on the length of the oligomeric chain and position of the functional groups. The spectra of all elements, within limits, on the steel surface was determined by energy-dispersive X-ray spectroscopy (EDX). Morphological changes on the electrode surface were monitored by scanning electron microscopy (SEM). The thermodynamic parameters such as the adsorption equilibrium constant (K-ads) and the free energy of adsorption (Delta G(ads)degrees) were calculated and discussed. Several adsorption isotherms were tested and the experimental data fitted well with the Langmuir adsorption isotherm. UV-visible spectral analysis of O-ANI solution containing LCS indicates the formation of Fe-N (ligand-metal) charge-transfer complex type interaction.