Uncaria Gambir As Natural Corrosion Inhibitor For Mild Steel In Acidic Solution

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dc.contributor.authorHussin, Mohd Hazwan
dc.date.accessioned2018-06-25T07:41:54Z
dc.date.available2018-06-25T07:41:54Z
dc.date.issued2010-09
dc.description.abstractUncaria gambir, a native Southeast Asia herbal plant has been characterized and studied as a mild steel corrosion inhibitor in acidic media. It was revealed that ethyl acetate gambir extract gave the highest condensed tannin, phenol and flavonoid content compared with other solvent extracts. Quantification studies by means of HPLC have shown that more than 80 % (wt) of gambir extract consists mainly of catechin. The effect of both ethyl acetate gambir extract and (+)-catechin hydrate as corrosion inhibitors for mild steel in 1 M HCl solution was done using various techniques such as weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. It was revealed that inhibition was concentration dependent as inhibition efficiency (IE) increases with the increase in the inhibitor concentration. Potentiodynamic polarization measurement indicated that the inhibitors act as “mixed-type” inhibitors with predominant anodic inhibition. EIS measurement indicated that the corrosion of mild steel in the absence and presence of inhibitor was mainly controlled by charge transfer process. The Randles-CPE model has been used as the equivalent circuit throughout this study. The optimum concentration obtained from all tests was at 1000 ppm (0.1 % wt). Temperature studies revealed that the corrosion rate of mild steel in the absence and presence of both inhibitors increases exponentially with temperature. Adsorption isotherm determination revealed that the inhibitor follows the Langmuir adsorption model. Surface analysis via SEM portrayed that there was a significant morphological improvement of mild steel surface in the presence of the inhibitor. The calculated value of free energy of adsorption, ΔGads and potential zero charge (PZC) for the inhibitors indicate that the inhibition mechanism process was spontaneous and the inhibitors were physically adsorbed (physiosorption) onto the mild steel surface.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/5777
dc.language.isoenen_US
dc.publisherUniversiti Sains Malaysiaen_US
dc.subjectUncaria gambir as natural corrosion inhibitoren_US
dc.subjectfor mild steel in acidic solutionen_US
dc.titleUncaria Gambir As Natural Corrosion Inhibitor For Mild Steel In Acidic Solutionen_US
dc.typeThesisen_US
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