STUDY OF EFFICIENCY OF NEPHELIUM LAPPACEUM (RAMBUTAN) PEEL EXTRACT AS AN ORGANIC INHIBITOR FOR API 5L GRADE X52M STEEL AND 5052 ALUMINUM IN 3,5% NACL SOLUTION

• Main Author: Tegar Alfaras, Dery
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85378
• Institution: Institut Teknologi Bandung

Corrosion is a spontaneous process of damage to metals and alloys caused by chemical, biochemical, and electrochemical interactions between the metal and its environment. Chloride ion is one of the most aggressive ions that causes corrosion, especially in seawater environments. One of the corrosion control methods that is currently being researched a lot is green corrosion inhibitors. Rambutan fruit peel extract is a natural green corrosion inhibitor that contains chemical compounds such as flavonoids and tannins which can decrease the corrosion rate. In this research, rambutan peel extract was studied as a corrosion inhibitor for API 5L Grade X52M steel and 5052 aluminum in a 3.5 wt% NaCl solution which is typically used as artificial sea water for laboratory experiments. Series of experiments were conducted to study the effect of adding rambutan peel extract inhibitors to reduce the corrosion rate on two different types of metals. The experiment began with making rambutan peel extract and preparing metal samples for immersion tests, electrochemical tests, and characterization tests. The immersion test in a 3.5% NaCl solution was carried out by varying concentrations of rambutan extract of 0 gpl, 2 gpl, 5 gpl, 7 gpl, and 9 gpl. Then, an electrochemical test were carried out which included Open circuit potential (OCP), electrochemical impedance (EIS), and potentiodynamic polarization (PDP) tests on a blank solution and a solution with a variable inhibitor concentration that produced the lowest corrosion rate. In addition, surface characterization analysis was carried out using an optical microscope (OM), 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, the highest efficiency of inhibitor to decrease corrosion rate for API 5L grade X52M with 5 gpl concentration are 75,154% for 7 hours of immersion time and 81,914% for 96 hours of immersion time. Meanwhile, for 5052 aluminum with 7 gpl concentration the highest efficiency are 62,166% for 7 hours of immersion time and 70,046% for 96 hours of immersion time. From the results of EIS method, the equivalen electrical circuit for blank solutions is RsCPEdl(Rct)-L and for inhibitor of rambutan peel extract solution is CPEi(Ri(CPEdl/Rp)). From the characterization with OM and SEM proves that inhibitors of rambutan peel extract can reduce the impact of corrosion on the surface of steel and aluminum alloys. Furthermore, from the characterization of organic compounds using FTIR and UV-Vis tests, it can be concluded that there are inhibitors of rambutan peel extract that are adsorbed onto the surface of steel and aluminum alloys.