Inhibition of Mild Steel Corrosion Using Aqueous Extract of Cocos nucifera L. Peduncle in Acidic Solutions and Their Adsorption Characteristics

Cocos nucifera L. peduncle (CNP) extract, obtained from destructive distillation, as a possible source of green inhibitor, for the corrosion of mild steel in 1 M HCI was evaluated using mass loss method, potentiodynamic polarization technique, and electrochemical impedance spectroscopy (EIS). The inhibition efficiency was found to change with variation in concentration of the inhibitor, time of immersion, and temperature. The adsorption of the inhibitor molecule onto the metal surface was found to obey El-Awady kinetic thermodynamic and Frumkin adsorption isotherm. The activation energy (E_a) and other thermodynamic parameters indicate a strong interaction between the inhibitor and the mild steel surface. Polarization measurements indicate that CNP act as a mixed type inhibitor. SEM confirmed the adsorption of inhibitor molecules on mild steel surface. Quantum chemical calculations were performed by Gaussian 03 code of programs using B3LYP /6-31 G (d) basis set, to gain some insight, about structural and electronic effects on the inhibition efficiency of the tested inhibitor. FT-IR spectral studies further corroborated the mechanism of inhibition.