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    Examination of Plated and Protective Coatings by Electrographic Analysis

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    The principles of electrographic analysis have been described elsewhere in this symposium. This paper will deal only with the application of electrographic analysis to the study of plated or coated surfaces, and more specifically to the examination of surfaces for the continuity of coatings or for the presence of holes. Electrographic analysis is often thought of as a method for either qualitative or semiquantitative tests for metals, but if one works with a tremendous diversity of metals and alloys, other methods are to be considered more reliable. For example, for qualitative tests the authors prefer spectrographic and X-ray diffraction analysis, and for quantitative or semiquantitative determinations they prefer spectrographic, polarographic, or chemical methods. But when one is concerned with studies on continuity of plated surfaces, protective coatings, or examination of position of one known metal in respect to another— the only practical and quick method is electrographic analysis. Using the same method as was described in other papers in this symposium, the sample is made positive, the electrode negative, and paper impregnated with electrolyte is used in between. If holes are present in the surface coating, a small amount of metal is transferred from the base metal into the paper by the passage of current. A color characteristic of the metal being tested for is then developed with an appropriate reagent. It is always known in advance, what the base metals and coatings are. The base material of course has to be an electrical conductor, but the coatings do not have to be. They may be metallic, inorganic, or organic coatings.

    Author Information:

    Galitzine, N.
    General Electric Co., Pittsfield, Mass.

    Ashley, S. E. Q.
    General Electric Co., Pittsfield, Mass.

    Committee/Subcommittee: E01.20

    DOI: 10.1520/STP47558S