EVALUATION OF INHIBITIVE PERFORMANCE OF AQUEOUS EXTRACT OF Dialium guineense ON CORROSION OF MILD STEEL IN 1.0 M HCl SOLUTION

Abstract

Aqueous extract of Dialium guineense (DG) leaves behaves as a green corrosion inhibitor to replace toxic chemicals. Inhibition of corrosion of mild steel in 1.0 M hydrochloric acid solution using weight loss method was studied at different temperatures ranged from 302K to 343 K. The inhibition efficiency is found to increase with increasing concentration of extract and decreases with rise in temperature. The maximum inhibition efficiency 77.77% was obtained at 313 K. The corrosion rate of mild steel increased from 302 K to 343 K but declined from 100 ppm to 1200 ppm of the aqueous extract of DG. The activation energy, thermodynamic parameters (free energy, enthalpy and entropy change) and kinetic parameters for inhibition process were also calculated. These thermodynamic and kinetic parameters indicate a strong interaction between the inhibitor and the metal surface. The adsorption of inhibitor on mild steel surface is exothermic, physical adsorption, and spontaneous reaction. Also adsorption of DG leaves extract on the surface of the mild steel follows Langmuir adsorption isotherm. The Langmuir adsorption isotherm was used to calculate the thermodynamic parameter ?Gads. The activation parameters Eact, ?Hact and ?Sact were calculated using Arrhenius equation.