OPTIMIZATION AND KINETIC STUDIES ON CORROSION CONTROL OF MILD STEEL USING IPOMOEA BATATAS LEAF EXTRACT AS INHIBITOR IN ACIDIC MEDIUM

AJANI,, DAVID OPEYEMI (2021) OPTIMIZATION AND KINETIC STUDIES ON CORROSION CONTROL OF MILD STEEL USING IPOMOEA BATATAS LEAF EXTRACT AS INHIBITOR IN ACIDIC MEDIUM. Masters thesis, Landmark University, Omu Aran, Kwara State.

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Abstract

Corrosion inhibitors routinely employed in industries are primarily toxic, posing a risk to persons and the environment; thus, green inhibitors made from plant extracts are required. The aim of the study is to investigate the optimization and kinetic studies of mild steel corrosion utilizing Ipomoea batatas Leaves extract (IBLE) as an inhibitor in phosphoric acid (H3PO4). The extract was subjected to a phytochemical screening to establish the presence of bioactive components. To optimize and study the interactions of the process factors, Box Behnken design was used. Temperature (30 - 60 oC), immersion period (5 - 10 days), inhibitor concentration (0.3 - 0.9 g/L), and acid concentration (0.5 - 1.5 M) are the variables employed in the experimental design. The corrosion inhibitory roles of various concentrations of the extracts were investigated using weight loss, electrochemical impedance spectroscopy, and potentiodynamic polarization techniques. Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Energy Dispersive X-ray Florescence (EDXRF) were used to characterize the samples. The presence of saponins, tannins, phenols, steroids, and glycosides in IBLE was confirmed by phytochemical analysis, which suggested the extract as a good inhibitor. The Temperature (45 oC), immersion time (5 days), inhibitor concentration (0.9 g/L), and acid concentration (1.0 M) from the experimental design, produced the highest inhibition efficiency of 99.60 %. The variables predicted for the validated optimal process level was (38 oC), immersion time (5 days), inhibitor concentration (0.9 g/L), and acid concentration (1.0 M) which yielded an inhibition efficiency of 99.8 %. Electrochemical impedance spectroscopy and potentiodynamic polarization inhibition efficiency were 95.47 % and 83.68 %, respectively. The SEM, FTIR, and EDXRF data revealed that the verified optimal procedure level produced more protective film on the coupon. The enthalpy ) was an endothermic reaction that occurred spontaneously. It was concluded that the Ipomoea batatas leaves extract served as a barrier, preventing the acid solution from corroding the mild steel. Keywords: Corrosion rate, inhibition efficiency, optimization and kinetics.

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