Line currents of unknown origin fluctuating as much as 20 amperes in upstream and downstream directions necessitated averaging from 20 to 30 measurements to get one of desired accuracy during coating conductance surveys on Trans-Mountain Oil Pipe Line Company's pipe line. The author postulates these currents may be of the same nature as those observed on other Canadian pipe lines and on lines in Texas, Oklahoma and Missouri, as well as on power systems in Canada and the United States. They are popularly attributed to sun spots, but may be due also to large adjacent bodies of ore. The currents make it extremely difficult for engineers to make reliable electrolysis surveys or tests of cathodic protection systems.

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Copyright 1954 by the National Association of Corrosion Engineers
1954
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