L51425 Interrupted Cathodic Protection as it Relates to SCC and Corrosion of Buried Pipelines.pdf

Since 1965, when stress-corrosion cracking was first generally recognized as a possible cause of failure in buried pipelines, the Pipeline Research Committee of the Pipeline Research Council International sponsored a research program at Battelle’s Columbus Laboratories to determine the causes of the cracking and to develop methods to prevent stress-corrosion cracking in the future. The causes are now fairly well understood, and much has been learned about possible preventive measures, but practical, well-accepted solutions to the problem have not yet been developed to the point where specific recommendations can be made. The problem is especially difficult for existing pipelines, for which there are considerably fewer options than for future pipelines.

In order to determine which of the possible benefits could be realized and how serious the possible problems would be, a research task was started at Battelle as part of the Stress-Corrosion-Cracking Phase of the NG-18 Program. The task on interrupted cathodic protection was divided into the following subtasks to answer specific questions about the feasibility of using interrupted cathodic protection to prevent or retard stress-corrosion cracking: Effect of interrupted currents on potentials under defective coatings ” Direct effect of potential cycles on stress corrosion cracking”” Effect of interrupted cathodic protection on the environment at the cathode”” Possibility of pitting and general corrosion during the off-portion of a cycle”” Field studies conducted by Henkels and McCoy to develop a device for interrupting the current and to evaluate the corrosion behavior of steel subjected to interrupted cathodic protection in the field”” Basic studies at the University of Newcastle upon Tyne to develop fundamental information to improve the understanding of the electrochemical phenomena associated with interrupted cathodic protection.

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