Corrosion Inhibitory Potential of Ethanol Extract of Senna obtusifolia on Mild Steel in 5M HCl

I. Ali, J. Yisa, J. O. Jacob


This study investigated the corrosion inhibition potential of Senna obtusifolia on electrochemical corrosion behavior of mild steel exposed to 5.0 M HCl. The results of the phytochemical screening revealed the presence of secondary metabolites such as flavonoid, tannins, anthraquinones, terpenoids, alkaloids, phenols and saponins. The FTIR result also revealed aromatics and functional groups such as R-OH, C=O, C-O and C-H which are attributes of good corrosion inhibitors. The effect of the extract as corrosion inhibitor was evaluated using gravimetric method at different concentrations of 0.1, 0.2, 0.3, 0.4, and 0.5 w/v respectively. The result revealed that Senna obtusifolia exhibits an inhibition efficiency of up to       87.64 % at extract concentration of 0.5 w/v. This could probably be due to the presence of the secondary metabolite and other functional groups revealed by both the phytochemical screening and FTIR spectrum that were present in the extract of Senna obtusifolia. Thermodynamics data generated suggested co-adsorption through a combination of both physisorption and chemisorption modes of interaction of the inhibitor. The negative free energy indicates that adsorption is spontaneous. The adsorption obeys both Langmuir and Freundlich adsorption isotherms. The degree of linearity is close to unity which indicates strong adsorption of the extracts on the mild steel. 

Keywords: Senna obtusifolia, corrosion inhibition, mild steel, HCl

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