Inhibition of corrosion of mild steel in well water by an aqueous extract of soapnut (Sapindus Trifoliatus)

Abstract

Inhibition efficiency of an aqueous extract of soapnut (Sapindus Trifoliatus) and Zn2+in controlling corrosion of mild steel in well water at room temperature has been evaluated by using weight loss method, polarization study and AC impedance spectra. Dynamic light scattering and Vickers hardness have also been employed. Weight loss method reveals that the formulation consisting of 10 ml soapnut extract and 50 ppm Zn2+ has 97 % inhibition efficiency in controlling corrosion of mild steel immersed in well water. Synergism parameters suggest that a synergistic effect exists between soapnut extract and Zn2+. Adsorption isotherm of metal surface obeys Langmuir adsorption isotherm. Polarization study reveals that the inhibitor system functions as anodic type of inhibitor. AC impedance spectra confirm the protective film formed on the metal surface. Dynamic light scattering (DLS) study reveals surface is in nano meter scale. The Vickers hardness of metal surface was increases in inhibitor system.