Microbiologically Influenced Corrosion in Copper and Nickel Seawater Piping Systems
1990
Little, Brenda J. | Wagner, Patricia A. | Jones, Joanne M. | McNeil, Michael B.
Presented at Annual Navy Corrosion Control Workshop (1st), Held in Key West, Florida in October 29-31, 1990.
Show more [+] Less [-]Sections of CDA 706 piping and Monel 400 tubing were severely pitted after exposure to marine and estuarine waters, respectively. Surfaces of both alloys were uniformly covered with thick surface deposits, ranging in color form blue-green to reddish brown to black. Pits developed under surface deposits containing 0.0001 - 0.00001 sulfate-reducing bacteria (SRB) in association with other bacteria. Pits were irregular in shape, lacking a consistent morphology. The observed 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 appear to have reacted selectively with iron and nickel in the alloys. Nickel has been selectivity removed from pitted areas leaving a copper rich spongy pit interior.
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