EFFECTIVITY OF GLUTAMIC ACID AS CORROSION INHIBITOR TOWARDS CARBON STEEL IN 1% NACL SOLUTION

• Main Author: Ketut Ketis, Ni
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/86009
• Institution: Institut Teknologi Bandung

Corrosion is one of serious problems in the petroleum mining. Alongside water, crude oil and natural gas also contain CO2, organic acid, such as acetic acid, sulfide compounds and chloride salts that have corrosive character towards the inner parts of carbon steel pipelines used to transport oil and natural gas in mining industry. Corrosion that occurs at the outer parts of pipelines can be protected by painting and cathode protection, whereas corrosion at the inner of pipelines should be prevented by the addition of corrosion inhibitor. There are two kinds of corrosion inhibitors, which are inorganic and organic inhibitors. Inorganic inhibitor have good efficiency of corrosion inhibition activity, however it can cause environmental problems due to its toxicity when accumulated. Therefore, the usage of organic inhibitor becomes a good alternative to prevent corrosion because it is more environmental friendly. Heteroatom organic compounds which contain nitrogen, oxygen, or sulfur atoms in its molecule structure, such as amino acids, can be used as corrosion inhibitor, because it can adsorb very well on metal surface. Amino acids, such as glutamic acid, have two carboxylic groups and one amine group that can perform corrosion inhibition activity at carbon steel surface. The aim of this research is to determine the effectiveness of glutamic acid as corrosion inhibitor towards carbon steel in 1% NaCl solution, which was saturated by CO2, utilizing Tafel method, performing the optimization of concentration, pH, and temperature. The pH optimization involves the usage of acetate buffer solution, which was prepared from various ratios of sodium acetate solution at constant concentration and acetic acid solution at various concentrations. In order to apply the results of this research as a model in teaching chemistry at high school regarding electrochemistry topic, it is not viable to perform the measurements of corrosion inhibitor activity utilizing Tafel method, therefore the corrosion inhibition activity analysis of glutamic acid towards iron nail was performed in agar medium. The results of this research showed that the optimum corrosion inhibition activity of glutamic acid was achieved at concentration of 8 ppm, which is 48,19% efficiency at room temperature (26oC). The functional group of glutamic acid which has dominant role in corrosion inhibition activity is carboxylic group from its side chain. The presence of acetate buffer solution in medium and higher temperature condition, did not give significant effect towards corrosion inhibition activity of 8 ppm glutamic acid in 1% NaCl solution. In the presence of higher pH of acetate buffer solution in medium, glutamic acid became corrosive towards carbon steel because it forms a protective layer which is less dense or porous compare to the condition at the lower pH of acetate buffer solution. At the lower pH of acetate buffer solution in medium, the concentration of acetate ion increased and formed a FeCO3.CH3COO– layer, which is denser or non porous, resulting the decrease in corrosion current. At higher temperature, the interaction between glutamic acid and iron on carbon steel surface is weaken, therefore the interaction between carbon steel surface and corrosive medium still occurred. The increase of temperature enforced glutamic acid to expel H+ ion resulting more corrosive medium and the increase of corrosion current. The corrosion inhibition ability of glutamic acid towards iron nail on agar medium showed significant results, therefore it was well understood the role of functional groups of glutamic acid in the formation of protective on iron nail surface which lead to the inhibition of corrosion rate. Glutamic acid at the concentration of 8 ppm is the most effective dosage to be used as corrosion inhibitor in 1% NaCl medium, saturated by CO2, at room temperature. In medium which contain acetate buffer solution and at higher temperature, glutamic acid is not effective to be used as inhibitor corrosion. In agar medium, glutamic acid showed good corrosion inhibition activity towards iron nail, therefore the experiment concerning the use of corrosion inhibitor, as one way to learn about corrosion and electrochemistry topic, can be applied at high school.