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The Corrosion Forum: Microbiological Induced Corrosion (MIC)

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    • CommentAuthormatco
    • CommentTimeJan 20th 2007
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    Bacterial corrosion-. One of the most troublesome forms of corrosion is localized corrosion on cast iron due to bacterial activities. Water mains can exhibit susceptibility to MIC as a result of their exposure to soil. In bacterial corrosion, attack is highly localized and confined to specific areas which develop into pits. Cast iron water mains are prone to this type of corrosion.

    Bacteria builds up a colony on cast iron which may act : (a) As a location for corrosion concentrations cells. (b) Formation of metabolic products such as sulfuric acid. (c) Interference in the cathodic process under oxygen free conditions by anaerobic bacteria.

    The prime bacteria that may be associated with the observed corrosion are the anaerobic sulfate reducers or sulfide formers.

    Sulfate reducers are strictly anaerobic, but nonetheless may be found in aerated soils. Slime deposits containing iron bacteria and harboring sulfate reducers have been found to corrode water mains as well. Analysis of soil for the presence of sulfides may indicate the presence of SRB.

    Iron bacteria represent a further distinct group. They obtain nutrition by oxidation of dissolved iron salts. Gallionella are aerobes, although they prefer limited oxygen. They tend to concentrate chlorides. They oxidize ferrous iron to insoluble ferric hydrate. High levels of iron, manganese and chlorides usually indicates the presence of iron bacteria. This type of bacteria usually causes internal corrosion.
    • CommentAuthordongibbon
    • CommentTimeFeb 19th 2007
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    I started working in the area of MIC some twenty years ago while working for Calgon Corp. I published a paper at the International Water Conference titled:" Case Study of Complex Pitting Corrosion on 316L Stainless Steel: the Role of Bacteria, Metallurgy and Water Chemsitry", IWC98-23, International Water, Journal of IWC, vol. 1, issue 2, pp 2-8, w. Wiatr and McGough. Chris Wiatr was the second author, but he contributed to the paper what I think is he best summay ever published of the microiology and biuochemistry of this complex problem. If anyone is interested in knowing the "ugly details" of these processes, this paper is the palce to go.

    Donald L. Gibbon
    MATCO Inc
    Materials Microcharacterization
    • CommentAuthorLaluc
    • CommentTimeFeb 22nd 2007
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    This is a new area for me. We discovered such corrosion on stainless steel tanks tansporting kaolin in water solutions. Where is-it possible to get information on this subject ? whre to get the document referered to by Donald L. Gibbon ?
  4.  permalink
    Houghton International offers a great line of Rust Preventative products that help to prevent MIC. To get more information on their full line of products, check out their website at www.houghtonintl.com.

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