Microbiologically Influenced Corrosion of Copper Alloys in Saline Waters Containing Sulfate-Reducing Bacteria
1991
Little, Brenda | Wagner, Patricia | Ray, Richard | Jones, Joanne M.
Sections of CDA 706 piping and Monel 400 tubing were severely pitted after exposure to marine and estuarine waters. Pits developed under surface deposits of mixed bacterial communities containing 100,000-1,000,000 sulfate- reducing bacteria (SRB). Localized corrosion was attributed to a combination of differential aeration cells, a large cathode: small anode surface area, concentration of chlorides, development of acidity within the pits and the specific reactions of the base metals with sulfides produced by the SRB. Chlorine and sulfur reacted selectively with the iron and nickel in the alloys. Nickel had been removed from the pitted areas leaving a copper-rich, spongy pit interior. SRB isolated from in-service corroding systems were used to inoculate copper- and nickel-containing foils for laboratory studies. Environmental scanning electron microscopy (ESEM) and energy dispersive x-ray analysis (EDS) were used to characterize the topography and chemical composition of the wet biofilm/corrosion layers. The thickness, tenacity and chemistry of the sulfide layers as well as the severity of localized corrosion varied among the alloys and mixed cultures.
Show more [+] Less [-]Pub. in Corrosion 1991, The NACE Annual Conference and Corrosion Show, Paper Number 101, p101/1-101/20, 11-15 Mar 1991.
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