Theoretical and Experimental Studies on the Adsorption of N- [(E)-Pyridin-2-ylmethylidene] Aniline, a Schiff Base, on Mild Steel Surface in Acid Media

Abstract

The adsorption of N-[(E)-Pyridin-2-ylmethylidene] aniline, a Schiff base, on to mild steel surface in 1M HCl and 0.5M H2SO4 solutions and the consequent corrosion protection were studied employing weight loss method, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. DFT calculations were performed to investigate its interaction with the metal surface at the atomic level to understand its inhibition mechanism. The adsorption process is well described by the Langmuir isotherm. The thermodynamic parameters indicated that the adsorption is spontaneous and the interaction of the inhibitor at the mild steel surface is mainly through physisorption. The Ra values obtained in AFM studies for the uninhibited and inhibited sample in HCl media respectively are 0.756 and 0.559 μm, and that in H2SO4 media are 0.411 and 0.406 μm. The lesser roughness values of the inhibited sample shows the adsorption of the molecules onto the mild surface. The inhibition efficiencies were found to improve with concentration of the inhibitor and the maximum efficiency was observed at 400ppm in all the investigation methods adopted. The inhibitor was found to exhibit a higher efficiency in HCl media (95.7%) than in H2SO4 (92.8%). The theoretical and experimental results are found to be in good agreement. Keywords: Corrosion, Inhibitor, Potential of Zero Charge, Atomic Force Microscopy, Density Functional Theory