STP1056

    Determination and Elimination of the Uncompensated Resistance in Low Conductivity Media

    Published: Jan 1990


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    Abstract

    The positive feedback and the interrupter technique have been used for the continuous elimination of the uncompensated resistance Ru during the recording of potentiodynamic polarization curves. The positive feedback technique was evaluated with a PAR model 173 potentiostat and a Solartron model 1286 potentiostat. The Solartron potentiostat was also used with the interrupter technique. The application of both techniques was initially evaluated with suitable dummy cells followed by the tests with steel and stainless steel in ethanolic hydrochloric acid (HCl) and in hydrazine. It was found that great care has to be used to determine the optimum parameters for the interrupter technique such as potentiostat bandwidth and interrupter frequency. The potential-time trace in the interrupter period needs to be observed on an oscilloscope in order to determine the optimum conditions. The saturated calomel electrode and similar reference electrodes cannot be used with the interrupter technique. Wire electrodes such as the silver/silver chloride (Ag/AgCl) or platinum give satisfactory results. The positive feedback technique is easier to use, however 100% compensation cannot be achieved in the PAR potentiostat. Since in most cases Ru will decrease during the recording of a polarization curve, it is difficult to obtain satisfactory results with this technique.

    Keywords:

    polarization curves, potentiostats, ohmic drop, positive feedback, interrupter technique, reference electrode, steel, stainless steel, hydrazine


    Author Information:

    Mansfeld, F
    Professor, graduate student, and research assistant professor, University of Southern California, Los Angeles, CA

    Chen, YC
    Professor, graduate student, and research assistant professor, University of Southern California, Los Angeles, CA

    Shih, H
    Professor, graduate student, and research assistant professor, University of Southern California, Los Angeles, CA


    Paper ID: STP25283S

    Committee/Subcommittee: G01.11

    DOI: 10.1520/STP25283S


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