STP978: Quantitative Assessment of Atmospheric Galvanic Corrosion

    Doyle, DP
    Joint researchers, Alcan International Research Centre, Kingston, Ontario

    Wright, TE
    Joint researchers, Alcan International Research Centre, Kingston, Ontario

    Pages: 13    Published: Jan 1988


    Abstract

    The test method for assessing galvanic corrosion that is described in this paper is applicable to bare metals. Its main advantages over existing techniques are that the results are quantitative and require only a short exposure period—typically 90 days—in the environment of interest. The test units are quite simple in concept, and experience has shown that the results are reliable and reproducible. Because the results are quantitative they are less subject to bias by the evaluator. The test units involve winding a wire of the anodic component of the galvanic couple onto the threads of a bolt of the cathodic member of the couple. The weight loss of the wire after a short exposure period relative to that of a similar wire wound onto a threaded plastic bolt gives a measure of the galvanic activity at any given location. The basic idea for the test unit was developed at Bell Telephone Laboratories over 30 years ago, but it has not achieved widespread acceptance as a test method. The present authors adopted the technique several years ago and have improved the laboratory procedures for assembling the test units and determining the weight losses of the wires. Many thousands of specimens have been exposed at a variety of locations around the world. The main emphasis in these tests was to measure the marine or industrial corrosivity components of the atmosphere, or both. Several technical papers have been written on the results of this application of the technique. In the present paper emphasis will be placed on the use of the technique to measure the amount of galvanic corrosion between different combinations of metals rather than its use to measure the corrosivity of the atmosphere. Because the work has been prepared by an aluminum producer, where galvanic corrosion is, naturally, a sensitive issue, there was emphasis on the behavior of aluminum in contact with several metals.

    Keywords:

    atmospheric corrosion testing, galvanic corrosion, quantitative assessment


    Paper ID: STP26196S

    Committee/Subcommittee: G01.07

    DOI: 10.1520/STP26196S


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