STUDY OF NEPHELIUM LAPPACEUM (RAMBUTAN) PEEL EXTRACT AS ORGANIC INHIBITOR FOR CORROSION CONTROL OF ASTM A36 STEEL IN HCL 1 M SOLUTION

• Main Author: Mahendra, Agung
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69416
• Institution: Institut Teknologi Bandung

Corrosion is a destructive phenomenon that can affect all metals and make disadvantages, especially at the cost. Therefore, we need to do some corrosion control to minimize the disadvantages. Corrosion inhibitor is one of the corrosion control methods that has been widely used. Nowadays, many research about corrosion inhibitors focuses on organic corrosion inhibitors, like fruit peels. Rambutan fruit peel is one of the organic wastes that can be found in Indonesia, so it is suitable to turn it into a corrosion inhibitor. Therefore, this research focused on the efficiency of rambutan peel extract as an organic corrosion inhibitor for ASTM A36 steel in HCl 1 M solution. This research used the immersion method, electrochemical method, surface characterization, and organic compound characterization. Immersion tests were carried out for 24 hours at room temperature and 6 hours at 30oC, 40oC, and 50oC with inhibitor concentrations of 0, 2, 4, 6, and 8 gpl. The results of the immersion test were used to analyze the adsorption isotherm model and inhibitor adsorption mechanism. Electrochemical tests involve open circuit potential (OCP) tests to measure the tendency of corrosion, electrochemical impedance spectroscopy (EIS) tests to measure inhibitor efficiency and equivalent circuit, and potentiodynamic polarization (PDP) tests to measure corrosion rate and identify inhibitor type. Lastly, there were surface characterization using a scanning electron microscope (SEM) and organic compound characterization using fourier-transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). Based on the immersion test, a higher inhibitor concentration gives a lower corrosion rate and a higher inhibitor efficiency up to the optimum concentration. The optimum inhibitor concentration was at 6 gpl with an efficiency of 92,6%. The isotherm adsorption models suitable for this research were Langmuir and Freundlich models. The change of adsorption free energy indicated that the adsorption mechanism of this inhibitor is physical adsorption (physisorption). OCP tests indicated that a system with an inhibitor tends to be less corroded than a system without an inhibitor. EIS tests indicated that the optimum inhibitor concentration was at 6 gpl with an efficiency of 86,9% and the equivalent circuit was [Rs- (Rp/CPE)]. PDP tests indicated that the optimum inhibitor concentration was at 6 gpl with an efficiency of 91,8% and this inhibitor can be identified as a mixed-type inhibitor from the difference in corrosion potential value. Surface characterizations using SEM indicated that this inhibitor could reduce the corrosive effect of hydrochloric acid on the steel surface. Organic compound characterizations using FTIR and UV-Vis indicated that the organic compound in the inhibitor plays a role in decreasing the corrosion rate of the steel.