Abstract

CORROSION INHIBITION BY AQUEOUS EXTRACT OF TEPHROSIA VILLOSA LEAVES

A. Samsath Begum, A. Jamal Abdul Nasser* and Susai Rajendran

Abstract

The present work aims to evaluate the inhibitive effect of Tephrosia villosa extracts to minimize the corrosion rate of mild steel in acidic medium. The study was finding a process of low cost and environmentally friendly also safe inhibitor to minimize the mild steel corrosion rate. Corrosion inhibition of mild steel in 1.0N HCl and 0.5M H2SO4 solution by Tephrosia villosa extract is achieved. The inhibition process is ascribed to the formation of an adsorbed layer of inhibitor on the surface of metal which prevent the metal from corrosion. The inhibition efficiency (%IE) and surface coverage (θ) of leaves extract of Tephrosia villosa increases with increase in concentration of inhibitor. Polarisation and impedance studies show that the inhibition efficiency increases with increase in inhibitor concentration. The maximum efficiency was observed to be 98.90% in 1.0N HCl and 97.64% in 0.5M H2SO4. The adsorption of leaves extract on the surface of mild steel was based to obey Langmuir and Tempkin isotherm. The free energy value (ΔGads) indicated that the adsorption inhibitor molecule was typical of physisorption. The results obtained show that Tephrosia villosa extract could serve as an excellent eco-friendly green corrosion inhibitor. This green inhibitor could find apposite applications in anodizing and coatings of metal surface.

Keywords: Tephrosia Villosa, Corrosion inhibitor, Mild Steel, Weight loss, Polarisation study, Impedance study, Langmuir & Tempkin adsorption isotherm.