<i>Costus afer</i> leave extract as nontoxic corrosion inhibitor for mild steel in H₂SO₄

Abstract

The corrosion inhibition performance of the ethanol extracts of Costus afer leaves (EECAL) on the corrosion of mild steel in 5 M H₂SO₄ solutions at 303K and elevated temperatures of 313, 323 and 333 K was investigated using weight loss method (gravimetric) and hydrogen evolution (gasometric) techniques respectively. The results indicate that the leave extract inhibit the corrosion of mild steel with maximum inhibition efficiency (93.1%) at 3.0g/L. Generally the inhibition efficiency was found to increase with increase in concentration of the leave extract but decreased with rise in temperature. Inhibition mechanism was deduced from the temperature dependence of the inhibition efficiency as well as from activation parameters that govern the process. Adsorption of the leave extract on the mild steel coupon was found to obey the Langmuir, Temkin, Frumkin and Freundlich adsorption isotherms.

KEYWORDS: Mild steel, Costus afer, Adsorption isotherm, Physical adsorption