Use of Sputter-Deposited 316L Stainless Steel Ultrathin Films for Microbial Influenced Corrosion Studies
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USE OF SPUTTER-DEPOSITED 316L STAINLESS STEEL ULTRATHIN FILMS FOR MICROBIAL INFLUENCED CORROSION STUDIES P.A. Suci*, A.J. Pedraza**, M.J. Godbole**, and G.G. Geesey* *Montana State University Department of Microbiology, Bozeman, MT "**University of Tennessee, Department of Materials Science, Knoxville, TN Abstract Ultra thin films (12nm) were sputter deposited onto cylindrical germanium internal reflection elements pre-coated with a thin (2nm) layer of Cr 20 3. Two crystals were inserted into Circle cell flow-through chambers and mounted on the optical bench of an Fourier Transform Infrared (FT-IR) spectrometer. One chamber was maintained as a sterile control while the other was sequentially inoculated with four bacterial species:Pseudomonas aeruginosa, Bacillus subtillis, Hafnia alvei, and Desulfovibriogigas, in that order. The water absorption band (1640cm-') was monitored and used to follow the deterioration of the ultra thin films. In this respect, the sterile control and inoculated films exhibited only slight differences during the 1000h course of the experiment. Assay of the visible biofilm that had accumulated on the surface of the inoculated crystal after 1000h revealed that the film incorporated viable cells from all four strains. Introduction In order to investigate microbial influenced corrosion (MIC) methodologies are required which can probe both fouling and corrosion processes as they occur, thus making the analysis of the interrelationships possible. It has been previously demonstrated that both bacterial colonization and deterioration of ultra thin films of copper deposited on germanium internal reflection elements (IRE) can be monitored in real-time using Fourier Transform Infrared (FT-IR) techniques [1]. In the present article some preliminary results are presented in which this methodology is adapted to the study of MIC of 316L stainless steel. Sulfate reducing bacteria (SRB) are well-known to be instrumental in promoting pitting corrosion of mild steel [2], and are thought to promote corrosion of passive steels as well [3]. In order for SRBs to colonize a surface they need to be provided with an anaerobic reducing environment. It has been shown that Desulfovibrio gigas can colonize a stainless steel surface which has been exposed sequentially to three bacterial species: Pseudomonas fluorescens, Bacillus subtillis, and Haftnia alvei [4]. In research presented here we have initiated the establishment of this four member consortium (substituting Pseudomonas aeruginosa for Pseudomonasfluorescense)on ultra thin films of 316L which were deposited on germanium IREs. The impact of this four member consortium on the thin films was investigated using methodology we developed to study MIC of copper. For our previous copper studies the films were vapor deposited onto the IREs. Vapor deposition is not suited for producing alloys of specified elemental composition because of the disparity in the melting temperatures of the component metals. A substantial part of the on-going effort in adapting our FT-IR techn
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