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Abstract
Biocorrosion inhibition of mild steel in the crude oil-water environment was investigated in the absence and presence of Carica papaya peel extract, Musa paradisiaca peel extract, and Moringa oleifera leaf extract as potential biocidal-green inhibitors using gravimetric, polarization, and surface analysis (Inverted metallurgical microscope and Fourier transform infra-red spectroscopy) methods. Kinetics and adsorption behaviors of the extracts were determined and evaluated. Results revealed that each of the extracts functioned as biocidal-green inhibitors in the crude oil-water environment and that biocorrosion inhibition efficiency (IE%) of each extract increased with increase in extract concentration and exposure time. Maximum IE% of 97.7, 96.5, and 99.2% was achieved with Musa paradisiaca peel extract, Moringa oleifera leaf extract, and Carica papaya peel extract, respectively, at 4000 mg/l extract concentration and 35 d exposure time. Polarization studies indicated that each of the extracts acts as a mixed-type inhibitor. Mild steel susceptibility to biocorrosion was significantly reduced by each of the extracts through biofilm development suppression and extract adsorption onto the mild steel surface which obeyed Langmuir, Freundlich, Temkin, and Flory-Huggins isotherm models. Kinetics of mild steel biocorrosion inhibition followed a Monod form of kinetics (Type A). Gibbs free energy of adsorption values for Musa paradisiaca peel extract (−9.65 kJ/mol), Moringa oleifera leaf extract (−9.57 kJ/mol), and Carica papaya peel extract (−9.71 kJ/mol) showed that each extract adsorption was spontaneous and of physical adsorption.
Disclosure statement
No potential conflict of interest was reported by the authors.