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Corrosion inhibition characteristics of Thymus vulgaris, Xylopia aethiopica and Zingiber officinale extracts on mild steel in H2SO4 solutions

P.C. Okafor (Corrosion and Electrochemistry Research Group, Department of Pure and Applied Chemistry, University of Calabar, Calabar, Nigeria)
E.A. Apebende (Corrosion and Electrochemistry Research Group, Department of Pure and Applied Chemistry, University of Calabar, Calabar, Nigeria)

Pigment & Resin Technology

ISSN: 0369-9420

Article publication date: 3 November 2014

Abstract

Purpose

This paper aims to evaluate the inhibitive action of the corrosion of mild steel in sulphuric acid solutions by ethanol extracts of Thymus vulgaris (TYV), Xylopia aethiopica (XYA) and Zingiber officinale (ZGO) as eco-friendly and non-toxic mild-steel corrosion inhibitors in H2SO4 solutions.

Design/methodology/approach

Ethanol extracts of TYV leaves, XYA fruits and ZGO roots were used as inhibitors in various corrosion tests. Gravimetric and gasometric techniques were used to characterize the mechanism of inhibition.

Findings

Results indicate that the extracts inhibit the corrosion process efficiently. Inhibition efficiency was found to increase with an increase in extract concentration and decrease with an increase in temperature. Inhibition efficiencies followed the trend TYV > ZGO > XYA. Thermodynamic considerations revealed that the energy of activation increased in the presence of the plant extracts. Adsorption of the plant extracts on mild steel surface occurred spontaneously, and Ea and ΔGads values confirm a physical adsorption processes. Phytochemical studies showed the presence of saponoids, flavonoids and polyphenols whose attachment to adsorption sites on the metal surface is responsible for the inhibition process. Experimental data fit the Langmuir adsorption isotherm.

Practical implications

The plant extracts can be used in chemical cleaning and picking processes.

Originality/value

The research provides information on the possible use of the ethanol extracts from TYV leaves, XYA fruits and ZGO roots as sources of cheap, eco-friendly and non-toxic corrosion inhibitors.

Keywords

Citation

Okafor, P.C. and Apebende, E.A. (2014), "Corrosion inhibition characteristics of Thymus vulgaris, Xylopia aethiopica and Zingiber officinale extracts on mild steel in H2SO4 solutions", Pigment & Resin Technology, Vol. 43 No. 6, pp. 357-364. https://doi.org/10.1108/PRT-07-2013-0060

Publisher

:

Emerald Group Publishing Limited

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