THE ISOLATION OF PROTEIN FROM LATEX HEVEA BRASILIENSIS AND THE DETERMINATION OF CORROSION INHIBITION ACTIVITY TOWARD CARBON STEEL

• Main Author: Zain, Ufaizah
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/85988
• Institution: Institut Teknologi Bandung

Carbon steel pipelines have been used to transport materials or product in industry. Petroleum industry is among the industries that utilized carbon steel pipelines. The presence of gasses such as CO2, O2 and H2S, as well as water in its environment, caused the corrosion towards the pipelines. Corrosion might occur at either inside or outside of the pipe. Corrosion which occurred at the outside parts of pipelines can be prevented by either coating or galvanic cell. On the other hand, corrosion which occurred at the inside parts of pipelines can be prevented by adding a corrosion inhibitor to its environment. Corrosion inhibitor can be defined as a chemical compound when added in small concentration to its environment would prevent or slow down corrosion rate. Corrosion inhibitors involve either inorganic or heteroatom organic compounds. Inorganic compounds such as chromates, phosphates and nitrites have not been used any longer because these compounds are toxic and can not be degraded in the earth that polluted environment. On the contrary, organic compounds is easier to be degraded and more environmental friendly. One of the organic compounds used as corrosion inhibitor is amino acid. Some research showed that amino acids such as proline, histidine and alanine, gave significant corrosion inhibition activity. The research also showed that amino acids which form peptide compounds gave better corrosion inhibition effect than single amino acid. Protein, which is amino acids polymer, is assumed to have comparable corrosion inhibition effect as much as amino acid and the peptide compounds. Latex, which is an extract isolated from rubber tree Hevea brasiliensis, has high economic value. Latex can be obtained by tapping the bark of rubber tree. Latex consisted of rubber particles and non rubber particles such as protein. However, in latex processing industry, the protein is not used and treated as waste because it can cause allergy to humans. The aim of this research is to utilize this protein as source of corrosion inhibitor towards carbon steel and therefore would enhance the economic value of protein latex. There are some methods to separate latex from other compounds; one of them is by coagulation of latex with 1 % acetic acid solution. The latex serum is consisted of many compounds including protein. The corrosion inhibition activity of serum was tested toward carbon steel. Subsequently, the serum was fractionated by the addition of ammonium sulphate solution. This fractionation produced 3 fractions as 60%, 80% and 90 % fraction. The determination corrosion inhibition activities toward carbon steel utilizing Tafel method. The results showed for each fraction, which is the 60%, 80% and 90% fraction, that the efficiency are as much as 66.56%, 44.32% and 33.96%, respectively. The serum showed corrosion inhibition efficiency as much as 87.63%. The corrosion inhibition efficiency of the serum is higher than its fractions. It was assumed that there are synergic effect resulted by all the components of proteins in these fractions. Besides protein, there are other components that supposed to give additional corrosion inhibition effect. However, most of the components are relatively not stable. This fact was proved by the measurement of corrosion inhibition activity of the serum which prolonged at different interval times. The measurements showed the decrease in corrosion inhibition efficiency of the serum when prolonged for 1, 7 and 21 days, which are 87.63%, 72.27% and 41.25%, respectively. The results of corrosion inhibition activity measurements of the protein fraction showed that the 60 % fraction gave the highest corrosion inhibition efficiency, whereas the 90% fraction gave the lowest result. The differences in corrosion inhibition efficiency of each fraction are due to the differences in size and weight of protein molecules of these fractions. In the fractionation process, protein with lower molecular weight will precipitate in ammonium sulphate in higher concentration; on other hand protein with higher molecular weight will precipitate in lower concentration. The higher molecular weight protein has more amino acids, therefore it has more polar groups, resulting more interaction possibility with Fe which gave higher corrosion inhibition efficiency. Based on the results, the size and weight of protein molecules are assumed to play important role in corrosion inhibition activity toward carbon steel. The stability of protein molecules also gave the influent to corrosion inhibition efficiency.