THE CORROSION OF CARBON STEEL IN ROCK MICROCOSMS CONTAINING NATIVE YUCCA MOUNTAIN MICROORGANISMS

摘要

Microorganisms implicated in microbially-influenced corrosion were isolated from the deep subsurface at Yucca Mountain, and include iron-oxidizing (FeOx), sulfate-reducing (SRB), and exopolysaccharide (EPS)-producing bacterial species. Various combinations of these microorganisms were inoculated into a test system composed of a 1020 carbon steel coupon immersed in a mixture of sterile rock and soft R2A agar prepared with simulated groundwater. A 1% KC1 bridge was used to connect the test system to a calomel reference electrode. A platinum counter electrode was used to apply a potential and the corrosion rate was measured by polarization resistance. Prior studies at ambient and elevated (50 ℃) temperatures demonstrated that these microorganisms were capable of corroding carbon steel. The current research investigated whether the presence of a rock surface enhanced the ability of the test microorganisms to survive elevated temperature and corrode carbon steel. Uninoculated electrochemical cells were prepared to monitor abiotic corrosion. Initial and weekly corrosion rates were obtained for the duration of the experiment. Upon completion of the experiment, the test system was dismantled and the coupons prepared for phospholipid fatty acid and microscopic analyses, to assess microbial biomass and bio film formation, respectively. Increased biomass and higher corrosion rates were observed in the rock/agar microcosms.