On Wednesday February 12th, 2013 the ICMT hosted Dr. Jeffrey Sowards from Applied Chemicals and Materials Division of National Institute of Standards and Technology in Boulder, Colorado.
Dr. Sowards gave a lecture on “Microbiologically Influenced Corrosion of Copper and Steel Alloys in the Presence of Acetobacter sp. in a Simulated UST Sump Environment”
Time: February 12, 2014 from 1:00pm – 3:00pm
Venue: Innovation Center, Room 103
Speaker Bio: Jeffrey Sowards is a Metallurgist in the Applied Chemicals and Materials Division at the National Institute of Standards and Technology in Boulder, Colorado. His research interests at NIST include studies of corrosion and its effects on mechanical property degradation of structural materials and fuel pipelines, determination of structure-property relationships of engineering alloys, and evaluation of welding and materials processing on microstructure and mechanical properties. He was an NRC Postdoctoral Research Associate at NIST, a graduate student and postdoctoral researcher at The Ohio State University, and a guest researcher at the Brazilian Synchrotron Light National Laboratory. He received B.S.W.E., M.S., and Ph.D. degrees from The Ohio State University where he studied welding metallurgy and corrosion.
Corrosion of underground storage tank (UST) sump components has been gaining recognition in recent years, particularly in the presence of alternative fuels such as fuel-grade ethanol (FGE) and ultra-low-sulfur diesel (ULSD). Usage of these fuels is projected to increase considerably over the next decade; thus, addressing the corrosion issues could be a major challenge facing the fuel storage and transport industries. Microbiologically influenced corrosion (MIC) is expected to be a significant contributor to corrosion of infrastructure alloys in alternative fuel environments because fuels are often biologically derived and conducive to supporting microbial growth. Acetobacter sp. is suspected to cause corrosion in UST systems since they convert carbon sources (e.g., FGE) into acetic acid, a volatile organic compound. Previous reports have demonstrated that acetic acid caused rapid corrosion of UST components, and that Acetobacter sp. make up the largest percentage of the microbial consortia in those environments.
In this work, we simulate corrosion of UST systems during headspace and aqueous exposure to biotic organic acid. Acetobacter sp. was inoculated into ethanol-water mixtures to induce corrosion during the metabolic conversion of ethanol into acetic acid. Carbon steel and copper were exposed to inoculum and volatile chemical species in the headspace over a period of approximately 30 days. The steel alloy exhibited pitting corrosion and the copper alloy exhibited pitting and intergranular corrosion due to biotic acetic acid. Corrosion rates were dependent on formation of corrosion products and are ranked as follows in order of increasing magnitude: Copper-aqueous < Steel-aqueous < Copper-headspace < Steel-headspace. The laboratory test method developed here reproduces corrosion observed in practice and could be used to test the efficacy of corrosion inhibitors and biocides in future studies.