Microbial Corrosion of Water Distribution Piping of a Petrochemical Plant

Several leakages were detected in a desalinated water (DSW) line in a petrochemical plant made from ASTM A106. The piping had been in service for only a few months. Samples of water were taken for laboratory investigations. Electrical resistance, pH, alkalinity, total hardness, sulfide, and chloride concentration of samples were measured to calculate the corrosivity of water and saturation indices (Langelier index, Ryznar index, aggressiveness index, and Puckorius index). Microbial field evaluations were conducted according to the NACE TM 0106 to recognize the presence of microorganisms. Results showed many acid-producing bacteria (APB) were present in the water. Fouling and corrosion products were analyzed by SEM, EDS, and XRD techniques. Results confirmed the presence of biofilms on the internal surface of the pipe, just nearby the corroded area. The morphology of the corroded surface was also analyzed by SEM. All evidence showed APB’s activities could be the most probable cause of piping failure.