Corrosion Inhibition and Adsorption Properties of Ethanol Extract of Vernonia Amygdalina for the Corrosion of Mild Steel in H₂SO₄

 

A.O. Odiongenyi,¹ S.A. Odoemelam,¹ N.O. Eddy^2,*

 

¹Department of Chemistry, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria

²Department of Chemistry, Ahmadu Bello University, Zaria, Kaduna State, Nigeria

 

Received 19 September 2008; accepted 4 December 2008

 

Abstract

Inhibitive and adsorption properties of ethanol extract of vernonia amygdalina for the corrosion of mild steel were studied using weight loss, thermometric, gasometric and IR methods of monitoring corrosion. The results revealed that ethanol extract of Vernonia amygdalina inhibited the corrosion of mild steel. The inhibition efficiency of the extract increased as the concentration of the extract increases. The inhibitor was found to function by being adsorbed on the surface of mild steel. The adsorption of the inhibitor followed the Langmuir adsorption isotherm. IR spectra of the corrosion product (without inhibitor), the extract and the corrosion product (with the inhibitor) confirmed that ethanol extract of vernonia amygdalina is an adsorption inhibitor. Phytochemical studies also revealed that ethanol vernonia amygdalina contains tannin, saponnins, flavanoid and anthraquinone, all of them contributing to the corrosion inhibition. Physical adsorption mechanism has been proposed from the values of some of the thermodynamic parameters obtained.

Keywords: corrosion inhibition, mild steel, adsorption, vernonia amygdalina.

 

 

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* Corresponding author. E-mail address: nabukeddy@yahoo.com