STP1232: Review of Effects of Biofilms on the Probability of Localized Corrosion of Stainless Steels in Seawater

    Salvago, G
    Professor and corrosion research engineer, CNR-ITM, Milano,

    Taccani, G
    Professor and corrosion research engineer, CNR-ITM, Milano,

    Fumagalli, G
    Doctor, CNR-CESPEL, Milano,

    Pages: 26    Published: Jan 1994


    Abstract

    Measurements have been made of pH values in the layer adjacent to finemeshed screens immersed in artificial and natural seawater. The results obtained on platinum, bronze, nickel-based alloys, stainless-steel and carbon-steel screens indicate that acidic environments can be formed beneath the biofilm on even cathodically polarized metallic materials. From an examination of data regarding the exposure of different materials in galvanic couples to natural and artificial environments, it seems clear that stainless steels exposed to the acidification of the artificial environment: (1) leads to depolarization phenomena of the cathodic processes, with effects qualitatively but not quantitatively similar to those observed in natural seawater; and (2) enhances the localized corrosion onset probability, though the attack penetration depth is lower than values observed in natural seawater.

    The different procedures for obtaining polarization curves in seawater, as well as the significance of the numeric values achieved, are discussed herein. The electrochemical complexity of biofilms is emphasized. Some aspects of the biofilms formed on stainless steel exposed to seawater are similar to those observed for conductive polymer films, such as polypyrroles.

    Keywords:

    marine corrosion, biofilm, pH, polypyrrole, stainless steel, electrochemical techniques, localized corrosion, microbiologically influenced corrosion (MIC)


    Paper ID: STP12926S

    Committee/Subcommittee: G01.09

    DOI: 10.1520/STP12926S


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