Browsing by Author "Onyima, Chukwuma"

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    Corrosion inhibition of mild steel in acidic solutions using moringa oleifera as inhibitor
    (Federal University of Technology, Owerri, 2019-09) Onyima, Chukwuma
    The corrosion behavior of mild steel in 1 M HCl and 0.5 M H2SO4 acidic environments was investigated using gravimetric and electrochemical techniques. The results obtained from both gravimetric and polarization experiments showed that mild steel is more susceptible to acid corrosion in 0.5 M H2SO4 than in 1 M HCl, with higher mass loss (gravimetric) and current density (polarization) obtained with sulphuric acid system compared to hydrochloric acid system. The effects of ethanol, sulphuric acid and water extracts of Moringa oleifera on the corrosion behavior of mild steel in the acid solutions were also analyzed. Generally, the different extracts exerted appreciable inhibition performance with sulphuric acid and water exhibiting higher inhibition efficiency than ethanol but ethanol exhibited higher stability in hydrochloric acid system. The trend of inhibition efficiency changed in sulphuric acid system with ethanol extract having the best performance than other extracts according to the polarization and temperature results, although, gravimetric data contradicted. Polarization studies revealed that the plant extracts functioned as mixed inhibition mechanism. Inhibition efficiency in general, increased with increase in the concentration of the extracts but decreased with prolonged exposure time. The discrepancies in the inhibition efficiencies exerted by the different extracts was attributed to the differences in the extracting abilities of the solvents, while discrepancies observed with the methods was attributed to time and instrumental effects. The Moringa oleifera leaf ethanol extract was characterized using gas chromatography / mass spectrometry (GC/MS). The analysis confirmed that the extract contained more than 29 active constituents including; 28.55% 9,12-Octadecadienoic acid (Z,Z)methyl ester; 11.24% n-Hexadecanoic acid; 9.31% 9,12,15-Octadecatrienoic acid methyl ester; 6.32% Benzeneacetonitrile,4-hydroxy-;5.6%2-Furancarboxaldehyde,5(hydroxyme- thyl)-;4.85%Heptadecane; 3.49% and others. Since the presence of some organic species in the extract has been confirmed by GC/MS, selected constituents of the extract were modeled in order to assess their adsorbability using the density functional theory (DFT) and the result revealed remarkable high interaction energies, which corroborate the experimental findings.