STUDY OF MICROBIOLOGICALLY INDUCED CORROSION OF 5083 ALUMINIUM ALLOY BY SULFATE-REDUCING BACTERIA IN SEAWATER

• Main Author: Putu Riska Agustina, Luh
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/68962
• Institution: Institut Teknologi Bandung

The main issue often occurs in the ship hull is corrosion. Although the primary material for ship hull has good corrosion resistance (AA5083), but still pitting corrosion inevitably happens. It’s because there are many chloride ions contained in seawater. The corrosion behavior of aluminium alloys in seawater is also influenced by the presence of bacteria that can accelerate or inhibit the corrosion process. This study aims to determine the influence of sulfate-reducing bacteria on the corrosion of AA5083 alloy in seawater. Bacillus aryabhattai use in this experiment as one of sulfate-reducing bacteria group and seawater comes from Santolo Beach, Garut, West Java. A series of experiments were carried out on anaerobic condition in seawater environment in the presence of sulfate-reducing bacteria. Immersion test, polarization test, and EIS were performed to determine the corrosion rate and polarization resistance of AA5083 alloy. Biofilm, a thin, slimy film of bacteria that adheres to a surface, was also analyzed using Fourier Transform Infra-Red (FTIR) and Scanning Electron Microscope (SEM). To determine the correlation of the bacterial phase at the corrosion rate, a calculation of sessile and planktonic bacteria is carried out in each time variation. After 14 days of immersion, the corrosion rate of the alloy in bacteria-added seawater was lower than that of the control seawater, based on the weight loss and polarization test. The corrosion rate values in the immersion test and polarization test are 0.0263 mmpy and 0.003 mmpy (medium with bacteria), respectively; 0.0348 mmpy and 0.0075 mmpy (control medium). The polarization resistance obtained from EIS also showed corresponding results, which is 82466 ? (medium with bacteria) and 11156 ? (control medium). The results of these experiments showed that the presence of sulfate-reducing bacteria slows down the corrosion process in the metal AA5083 surface. It is known afterward that the mechanism of this deceleration process has to do with the formation of biofilm layer on the surface of AA5083.