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

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.

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.

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 E_a and ΔG_ads 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.

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

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.