Anticorrosive assay-guided isolation of active phytoconstituents from Anthemis pseudocotula extracts and a detailed study of their effects on the corrosion of mild steel in acidic media

In this study, anticorrosive properties of various extracts (methanolic, aqueous methanolic and water extracts) of Anthemis pseudocotula for mild steel in 1.0 M HCl media is screened for the first time. Among the various tested extracts, the methanolic extract of A. pseudocotula shows the highest corrosion inhibition activity. Anticorrosive assay-guided isolation of this methanolic extract results in the isolation of a highly potent anticorrosive compound, APB (luteolin-7-O-beta-D-glucoside). The anticorrosive effects of APB on mild steel in 1.0 M HCl media were evaluated in detail using gravimetric, Tafel plots, linear polarization, electrochemical impedance spectroscopy and SEM and EDS techniques. Tafel plots reveal that APB acts as a mixed-type inhibitor. The adsorption behaviour of this green inhibitor on the mild-steel surface obeys the Langmuir adsorption isotherm. A surface morphology study through SEM and EDS analysis displays a noteworthy upgraded surface morphology of the mild steel plate in the presence of the green inhibitor in 1.0 M HCl media. The results obtained from electrochemical tests and weight loss measurements are in good agreement which shows excellent inhibition efficiency for the natural compound APB.