Evaluation of Corrosion Inhibition of Aluminium in Hydrochloric Acid Solution by Methanolic Extract of Vernonia amygdalina

International Journal of Chemistry | Vol. 2, No. 2, February 2011 | pp. 18–26

DOI: 10.46882/2011/IJC/000027

Article Type: Original Research Paper

Title: Evaluation of Corrosion Inhibition of Aluminium in Hydrochloric Acid Solution by Methanolic Extract of Vernonia amygdalina

Names of Authors: C. E. Odo¹, J. C. Ifemeje²*

Authors’ Affiliations:
¹Department of Biochemistry, Michael Okpara University of Agriculture, Umudike, Nigeria.
²Department of Biochemistry, Chukwuemeka Odumegwu Ojukwu University, Uli, Nigeria.

Abstract: The corrosion of aluminum equipment during industrial pickling and acid cleaning processes leads to significant structural damage, demanding the development of non-toxic plant-derived inhibitors. This investigation evaluates the corrosion inhibition performance of the methanolic extract of Vernonia amygdalina (Bitter leaf) leaves on aluminum coupons in 1.0 M HCl solutions. Experimental monitoring was conducted using gravimetric (weight loss) and gasometric methods at temperatures ranging from 303 K to 323 K. The weight loss results proved that the extract acts as an efficient corrosion inhibitor, showing a maximum inhibition efficiency of 88.6% at an optimum concentration of 2.0 g/L. The corrosion rate decreased with increasing inhibitor dose but increased with rising system temperatures. Activation energy values (Ea) calculated using the Arrhenius expression increased from 34.5 kJ/mol in blank acid to 68.2 kJ/mol in the presence of 2.0 g/L extract, indicating a physical adsorption mechanism on the aluminum surface. The adsorption path fit the Freundlich adsorption isotherm model with a negative Gibbs free energy of adsorption (delta G°ads = -18.4 kJ/mol), confirming a spontaneous process. Phytochemical tracking revealed that the presence of saponins and flavonoids drives the formation of this protective organic barrier layer.

Keywords: Aluminum; Acid corrosion; Vernonia amygdalina; Green inhibitor; Activation energy; Adsorption isotherm

Manuscript Timeline: Received: November 05, 2010; Revised: December 14, 2010; Accepted: January 05, 2011; Published: February 02, 2011.

Citation: Odo, C. E., & Ifemeje, J. C. (2011). Evaluation of Corrosion Inhibition of Aluminium in Hydrochloric Acid Solution by Methanolic Extract of Vernonia amygdalina. International Journal of Chemistry, 2(2), 18–26.

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