Adsorption and Corrosion Inhibtion of Gnetum africana Leaves Extract on Carbon Steel

Adsorption of Gnetum africana leaves extract and corrosion inhibition of carbon steel in hydrochloric acid solutions have been investigated using gravimetric technique. Inhibition efficiency increased with extract concentration and time of exposure. The effect of temperature on the corrosion behavior of mild steel in 1.0 M HCl with addition of plant extracts was studied at the temperature range of 303–333±1K. Inhibition efficiency of 92.42% was obtained. An adsorption mechanism involving physisorption and chemisorptions of extract constituents at low and high temperatures, respectively, has been proposed from the trend of adsorption free energies. The experimental data complied to the Langmuir and Temkin adsorption isotherms and the negative values of the Gibb’s free energy of adsorption obtained suggested that inhibitor molecules have been spontaneously adsorbed onto the C-steel.