The “electrical boundary” of a galvanic couple immersed in an aqueous medium, when corroding normally and also when corrosion is stopped by cathodic protection, is discussed in the light of present theory. Experimental data, consisting of potential measurements made on bimetallic couples in an unrestricted medium producing relatively little polarization and also one producing considerable polarization, are compared with theoretical data. The electrical boundary is theoretically defined and experimentally verified for model galvanic couples having bimetallic electrodes, one couple simulating line electrodes and the others having electrodes made of longitudinal cylindrical segments arranged in three anode-to-cathode area ratios. The effect on potential measurements as a result of interference to the normal flow of galvanic and external currents is also shown by experimental data. The results of this study indicate that geometric factors should be given consideration in making potential measurements on subsurface structures of similar configuration, such as cylindrical tanks and pipelines.

Subject
Anode potential, Cathodic protection, Cathodic potential, Cathodic current, Walls, Reference electrodes, Pipelines, Potential measurements, Electrochemical current, Galvanic current, Electrodes, Galvanic couple, Electrode potential
Copyright 1955 by the National Association of Corrosion Engineers.
1955
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