Corrosion inhibition characteristics ofThymus vulgaris,Xylopia aethiopicaandZingiber officinaleextracts on mild steel in H2SO4solutions

Abstract

PurposeThis paper aims to evaluate the inhibitive action of the corrosion of mild steel in sulphuric acid solutions by ethanol extracts ofThymus vulgaris(TYV),Xylopia aethiopica(XYA) andZingiber officinale(ZGO) as eco-friendly and non-toxic mild-steel corrosion inhibitors in H2SO4solutions.Design/methodology/approachEthanol 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.FindingsResults 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, andEaand ΔGadsvalues 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 implicationsThe plant extracts can be used in chemical cleaning and picking processes.Originality/valueThe 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.