#TITLE_ALTERNATIVE#

• Main Author: YULMARLIANI SUDARMAN ( NIM : 10511054 ), ASTRI
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/21298
• Institution: Institut Teknologi Bandung

The studies on green corrosion inhibitor were currently developed as an alternative of organic corrosion inhibitors. Catechins which are contained in green tea leaves can be developed to be used as green corrosion inhibitor. Catechin used in this research has been isolated from green tea leaves from tea plantation in West Java. The aims of this study is to isolate the catechin from green tea and then subsequently examined as corrosion inhibitor on carbon steel in 1% NaCl solution saturated by CO2 gas. The separation and purification techniques were performed by liquid-liquid extraction method. The green tea extract which has been isolated from green tea leaves resulting a yield of 10.91%, but the extract also contained another compounds hence need to be further purified. After purification processes, the results showed that the extract contained two major compounds: catechin and caffeine. The isolated catechin is a yellowish brown crystal with 66.92% in yields, while the isolated caffeine is a yellowish crystal with 4.39% in yields. The isolated compounds were analyzed and characterized using Thin Layer Chromatography (TLC), High Performance Liquid Chromatography (HPLC), IR spectroscopy, Liquid Chromatography-Mass Spectroscopy (LC-MS), and 1H-NMR spectroscopy. All the spectroscopy daya analysis confirmed that catechin and caffeine have been successfully isolated, which was also proven by the peaks in mass spectra showed at [M+H]+ 459.31 and [M+H]+ 195.16 corresponding to epigallocatechin gallate (EGCG) and caffeine, respectively. The ability of green tea extract, catechin, and caffeine to inhibit the corrosion on carbon steel in 1% NaCl saturated by CO2 environment was determined using the EIS (Electrochemical Impendance Spectroscopy) and Tafel extrapolation methods at various temperatures of 30, 45, and 60 0C with the variation in green tea extract concentrations of 200, 400, 600, 800, and 1000 ppm, as well as the variation in catechin and caffeine concentrations of 10, 25, 50, 75, and 100 ppm. The green tea extract showed its highest inhibition efficiency of 86.46% at 1000 ppm and temperature of 60 0C, while the highest inhibition efficiencies of catechin and caffeine were achieved at 100 ppm and temperature of 45 0C which are 67.80% and 49.79%, respectively. The values of the Gibbs adsorption free energy, Gads, at 45 oC for catechin and caffeine are -38.11 kJ/mol and -33.13 kJ/mol, respectively, which indicated that the adsorption process of both compounds onto carbon steel surface in 1% NaCl saturated by CO2 occurred semi-physically or semi-chemically. The results of Tafel extrapolation graphs showed that green tea extract and caffeine performed as anodic inhibitor, while catechin as ohmic inhibitor.