Cold rolled carbon steel (1018) is a commonly used structural material in various applications, including the construction of fuel storage tanks for naval ships. Desulfoglaeba alkanexedens (strain ALDCT) is a known fuel-degrading, anaerobic, sulfate-reducing bacterium (SRB) [1, 2] that thrives at fuel-water interfaces in marine environments and can influence the pitting corrosion of carbon steel. It has long been postulated that MnS inclusions in carbon steel can act as sites of pitting initiation [3]. The propagation of pitting corrosion is relatively well understood; however, the initiation of pits is still a subject of controversy [4, 5]. A careful study of pit initiation and propagation associated with sulfide inclusions, particularly as they relate to microbial influenced corrosion (MIC) under anaerobic conditions, has been lacking, partly because these inclusions are mostly submicron-sized and the evolution of their corrosion is difficult to monitor. The use of nanoprobes instead of microprobes is required to determine the elemental and chemical composition and to map out the elemental distributions at the submicron scale. Quantitative surface sensitive techniques such as Auger electron spectroscopy [4, 5] are essential for monitoring the nanoscale changes associated with surface-related phenomena, including MIC. This presentation will review the results of comprehensive and systematic studies of nano-inclusions on carbon steel surfaces prior to and following exposure of the steel to a solution of a mature ALDCT culture and to abiotic sulfide as a control. The nano-inclusions were carefully characterized using a field emission Auger nanoprobe with a spatial resolution of approximately 10 nm for imaging and spectroscopy and compared with results obtained using X-ray microprobes, which typically have a spatial resolution of around 1000 nm for spectroscopy and 10 nm for imaging. The study elucidates biologically driven corrosion reactions taking place in and around nano-inclusions. The impact of this fundamental analysis on the understanding of MIC phenomenon will be discussed.

References:

1. Davidova, I.A., et al., International Journal of Systematic and Evolutionary Microbiology, 2006. 56: p. 2737-2742.

2. Morris, B.E.L., J.M. Suflita, and H.H. Richnow, Geochimica Et Cosmochimica Acta, 2009. 73(13): p. A907-A907.

3. G, Waglen. Corrosion Science, 1974. 14: p. 331-349.

4. P. Schmuki, H. Hildebrand, A. Friedrich andS. Virtanen, Corrosion Science, 2005. 47: p. 1239-1250.

5. J.E. Castle and Ruoru Ke, Corrosion Science, 1990. 30(4/5): p. 409-428.

6. Support of ONR/MURI Grant No N00014-10-0946 is gratefully acknowledged.