STUDY OF BIOCORROSION BEHAVIOUR OF ALLOY AA 5083 BY THE BACTERIUM Citrobacter youngae SKC-5 IN MARINE ENVIRONMENT

• Main Author: EL FAKHRI (NIM : 12513003), FAJRIL
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/27120
• Institution: Institut Teknologi Bandung

Indonesia is referred to as the largest archipelago in the world, whose the sea surface covers an area of approximately 81%. This thus leads to most commodities transported by ships. The problem that often occurs with ships is leakage of vessels due to corrosion in marine environment. Aluminium alloy 5083 (AA-5083) is an alloy which is often used in the hull of ships. In normal environment, AA-5083 has high corrosion resistance because this alloy can form oxide layers (passive layers). However, the presence of Cl&#8722;ions in marine environment can damage the passive layers and causes pitting corrosion. Currently, many corrosion studies have been developed by forming biofilms of microorganisms on metal surfaces. One of the bacteria that can form biofilms is the iron- and sulfur-oxidizing bacteria. However, the biofilms can also increase the rate of corrosion under certain condition. Therefore, this study was conducted to determine the effect of the bacterium capable of oxidizing iron and sulfur, Citrobacter youngae SKC-5, on corrosion behavior of alloy AA-5083 in marine environment. <br /> <br /> <br /> <br /> Biocorrosion experiments began with the preparation of specimens which included cutting, sanding, and sterilizing specimens with alcohol. Especially for electrochemical testing, material was soldered with copper wire and then mounted and followed by sanding and sterilizing with alcohol. For seawater preparation, seawater was filtered and followed by sterilization using an autoclave. Furthermore, the bacterial culture of Citrobacter youngae SKC-5 was performed by inoculating it into the modified LB medium for 3 days 4 hours of incubation. Biocorrosion experiments were carried out in sterile seawater medium containing the bacterium Citrobacter youngae SKC-5 and then immersed for 7, 14, and 30 days to study the bacterial effect on corrosion rate, corrosion potential, corrosion current density, corrosion resistance, and corroded specimen surface. <br /> <br /> <br /> <br /> The results of the experiment showed that the corrosion current densities of AA5083 in seawater medium containing the bacterium Citrobacter youngae SKC-5 on day 7, 14, and 30 were 1.669 x 10-6 A/cm2, 1.771 x 10-7 A/cm2, and 1.689 x 10-6 A/cm2, respectively. The current densities in seawater medium with bacteria were observed to be lower than those in seawater medium without bacteria (3.887 x 10-6A/cm2, 1.020 x 10-5A/cm2, and 4.091 x 10-5A/cm2, respectively). SEM-EDS mapping and = FTIR analysis showed that biofilm layers were formed on AA-5083 specimen surface immersed in seawater medium containing bacteria. From the results of this study, it can be concluded that the bacterium Citrobacter youngae <br /> <br /> SKC-5 is able to inhibit the corrosion process of alloy AA-5083 in marine environment. <br />