ADSORPTION MECHANISM AND SYNERGISTIC INHIBITIVE EFFECT OF Telfairia occidentalis FOR THE CORROSION OF MILD STEEL IN HCl

J.T. Nwabanne¹, V.N. Okafor¹ and L.O.Chima²

Department of Chemical Engineering¹ and Department of Mechanical Engineering²

Nnamdi Azikiwe University, Awka, Nigeria

E-mail: joe_nwabanne@yahoo.com

ABSTRACT

The extract from the leaves of Telfairia occidentalis was investigated as corrosion inhibitor in 1MHCL solution using gravimetric technique at the temperature range of 303-333K. The joint effect of iodide ion and extract of Telfairia occidentalis was also investigated. From the result obtained, values of inhibition efficiency ranged from 44.3 to 89.8%, 63.4 to 90.07%, 80.4 to 91.63% and 82.6 to 94.0% at temperature of 303, 313, 323 and 333K respectively, showing that inhibition efficiency of the extract of Telfairia occidentalis increased with increasing temperature. The increase in inhibition efficiency as temperature increased suggests that mechanism of adsorption is chemisorption.  Also, the inhibition efficiency of the extract increased synergistically on addition of potassium iodide (KI). The inhibition potential of extract of Telfairia occidentalis is attributed to presence of tannin, phlobatannin, flavonoid, alkaloid, cyanogenic glycosides and amino acid in the extract. The heat of adsorption value obtained ranged from 51.70 to 33.89KJ mol^-1 indicating the adsorption of the inhibitor on surface of mild steel is endothermic. The adsorption behavior of the inhibitor was well described by Langmuir and Frumkin isotherm models.

Keywords: Corrosion, mild steel, inhibition, adsorption, Telfairia occidentalis.