A Critical Review of the Contribution of R&D to the Prediction and Management of SCC on Underground Pipelines

Much has been learned about the mechanism of the external SCC of underground pipelines since the first incident in the 1960’s.  A great deal of understanding has been derived from laboratory-based R&D studies regarding the mechanisms of both high-pH and the more-recently recognized near-neutral pH SCC.  A major focus of this work has been the development of models for predicting where and when SCC may occur, which in turn allow pipeline companies to develop methods for managing the problem.
The paper will highlight some of the successes of the R&D studies, including the identification of the important effect of temperature for high-pH SCC and the role of cyclic loading and crack-tip strain rate for both forms of cracking.  In turn, this information has lead the industry to install after-coolers at compressor stations to reduce the rate of crack growth for high-pH SCC and to develop corrosion fatigue-based models to predict the probability of failure as a function of operational parameters for the near-neutral pH form of cracking.  Other examples of the successful implementation of R&D will be discussed, as will areas in which the R&D community has been less successful.