The inhibition capacity of Brassica oleracea (BO) extract on the corrosion of pipeline steel in 0.5 M H 2 SO 4 was evaluated using electrochemical techniques. The results showed an excellent inhibition efficiency which increased with initial increase in extract concentration and temperature to a point and decreased with further increase in BO extract concentration and temperature. Mixed inhibition behaviour was proposed for the action of BO. The unique behaviour of BO was attributed to the organic entities present in the extract.

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The inhibitive action of Piper guineense (uziza leaf) extract on the corrosion of mild steel in a 2 M H2SO4 medium has been studied using weight loss method. The collected leaf samples were rigorously grounded and squeezed, with the resultant gel extract used for the weight loss determination at 1.0%, 2.0%, 3.0%, 4.0% and 5.0% v/v concentrations, respectively. Therefore, rectangular mild steel coupons in a 2 M H2SO4 solution were also employed to determine the amount of weight loss in the absence and presence of Piper guineense extract at temperatures of 303 K, 313 K and 323 K. The results show that mild steel corrosion inhibition increases with increasing concentrations of Piper guineense extract, showing greater efficiency at higher temperatures of 313 K and 323 K. Moreover, Piper guineense extract can effectively perform as a green and non-toxic inhibitor for mild steel corrosion in acidic environments.

The corrosion inhibition characteristics of Chrysophyllum cainto cotyledon aqueous extract was studied for the corrosion of pipeline steel in 0.5 M HCl using gravimetric technique. The corrosion surface morphology and corrosion surface film were studied using Scanning electron microscope and Fourier transform infrared spectroscopy respectively. The results obtained showed Chrysophyllum cainto aqueous extract as a good corrosion inhibitors of pipeline steel corrosion in acidic environment, recording an average corrosion inhibition efficiency above 90% at 303 K. The Scanning electron micrograph showed a smoother corrosion surface morphology in the presence of the extract while the Fourier transform infrared spectroscopic data showed the corrosion inhibition mechanism to be through adsorption.