EFFECT OF NEPHELIUM LAPPACEUM (RAMBUTAN) FRUIT PEEL EXTRACT AS CORROSION INHIBITOR FOR ALUMINIUM ALLOY 5052 IN HCL SOLUTION

• Main Author: Ketut Trisna Pramudia, I
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76149
• Institution: Institut Teknologi Bandung

Aluminium is the second most widely used metal in the world. Aluminum has the advantages of being lightweight, strong, flexible, and recyclable. Despite its many advantages, aluminum is also subject to corrosion. Corrosion protection can be done with the use of inhibitors. The use of inhibitors as corrosion inhibitors can use inorganic or organic inhibitors. Organic inhibitors, especially green inhibitors derived from plants, are subjects that have received a lot of attention. food waste such as fruit peel can be utilized as green inhibitor. Rambutan peel contains flavonoids and tannins which are proven to play an active role in the corrosion inhibition process. Therefore, this research studied the effect of rambutan peel extract as a corrosion inhibitor for aluminum alloy 5052 in HCl solution. The rambutan peel extract was prepared from maceration with 96% ethanol solution for 48 hours. A series of experiments were conducted in 0.5 M HCl test solution with varying concentrations of 0, 2, 5, 8, 10, and 15 g/L rambutan peel extract. Samples were subjected to immersion tests, electrochemical tests, and characterization tests. Immersion tests were conducted at a temperature variation of 25°C for 24 hours and 35°C, 45°C, and 65°C for 6 hours to determine the corrosion rate, inhibitor efficiency, adsorption isothermal model, and thermodynamic parameters. Electrochemical tests including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) were conducted to determine the type of inhibitor and the equivalent electrical circuit model. Surface characterization tests were conducted using optical microscope (OM) and scanning electron microscope- energy dispersive x-ray spectroscopy (SEM-EDS). Organic compound characterization tests included fourier-transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). The immersion test showed a decrease in corrosion rate and an increase in efficiency as the concentration of inhibitor added increased. The lowest corrosion rate obtained was 3.453 mm/year with an efficiency of 84.193% at a concentration of 15 g/L. The adsorption isotherm model follows Langmuir model with a physisorption mechanism in the range of ?Gads values -15.741 to -20.843 kJ/mol. The thermodynamic parameters of activation energy (Ea), enthalpy change (?H*), and entropy change (?S*) were increased as the inhibitor concentration increased. In the electrochemical test, it is known that the inhibitor is a mixed type inhibitor and the equivalent electrical circuit model Rs-(CPE/Rct/(RL-L))-L. In the surface characterization test, it is known that the surface of aluminum alloy smoother and there more carbon elements on the surface of aluminum alloy with inhibitor than without inhibitor. The corrosion product characterization test results proved that rambutan peel extract was adsorbed on the aluminum alloy surface.