Inhibition Activity of Ethanol Extract from Garlic (Allium sativum) toward Carbon Steel Corrosion in CO2 -Saturated Aqueous HCl

• Main Author: R Rahayu Putricana Azis, R
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/38065
• Institution: Institut Teknologi Bandung

Corrosion is a degradation process of metal or alloy by reaction of its environment. In the oil and natural gas industry, crude oil or gas fluid also contains water, dissolved salts, CO2, H2S, and organic acids, flow through carbon steel pipelines, thus aggressive corrosion on the inner surface of the carbon steel pipelines. Prevention of corrosion on the inner pipelines of carbon steel is most efficient by injection of corrosion inhibitor. Garlic contains antioxidant compounds that can be used as corrosion inhibitor (green inhibitor). This study used ethanol 96% for extraction process of the compounds from garlic by maceration for 4 days. The extract was then filtrated and concentrated under reduced pressure using rotary evaporator. Concentrated extract was re-extracted with ethyl acetate. Then ethyl acetate phase was evaporated under reduced pressure using rotary evaporator and aqueous phase was dried using freeze dry thus obtained dried garlic extract. FTIR (Fourier Transform Infrared Spectroscopy) results of both phase showed the peaks are presence of heteroatom, there is vibration peak of C=C (alkene) at wave number of 1638 cm-1 (ethyl acetate phase) and 1631 cm-1 (aqueous phase), then S=O group at wave number of 1132 cm-1 (ethyl acetate and aqueous phase), and S-C group at wave number of 815 cm-1 (ethyl acetate phase) and 827 cm-1 (aqueous phase). UV-Vis spectroscopy spectrum of aqueous phase showed the peak at ?max 443 nm. Antioxidant activity using DPPH (2,2-diphenyl-1-picrylhydrazyl) showed that garlic extract is a weak antioxidant with IC50 156.49. Qualitative corrosion test using nails give a positive result that the extract has a corrosion inhibition activities. Based on measurement of Electrochemical Impedance Spectroscopy (EIS) method with variation of concentration are 10, 30, 50, 70, 100, and 120 ppm, environment concentration of HCl are 0.1 M, 0.5 M, and 1 M, then temperature variation are 25 °C, 45 °C, 55 °C, and 65 °C, it was obtained the best percentage of corrosion inhibition efficiency (EI%) is 47.10% at 120 ppm of extract with temperature is 45 °C and 1 M of HCl environment. Then based on measurement of Tafel extrapolation obtained that garlic extract is mixed inhibitor.