Advanced materials development for safer energy pipelines

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Compromise of a material's structural integrity caused by corrosion is a common problem in industrial applications that require metals to be exposed to chemical environments. Depending on the metal's industrial in-service use, different forms of corrosion exist and, depending on the exposure environment, some may be more deleterious than others; for example, corrosion localized within an occluded region (i.e., under gaskets) compared to uniform corrosion on an entirely exposed alloy surface. Because of its insidious nature, localized corrosion may be difficult to identify and corrosion rates are usually only estimates since the electrochemical properties of the actively corroding region are difficult to measure. Within the oil and gas industry the most damaging form of localized corrosion is Stress-Corrosion Cracking (SCC), which is encountered in pipelines that are subjected to an applied stress while exposed to a corrosive chemical environment. SCC's impact on pipeline degradation will be investigated by replicating experimentally the combination of stress and chemical environments anticipated on in-service pipelines in Canada. Experimental resources from NOVA Chemicals (Calgary AB and Sarnia ON) and Western University (London ON) will be utilized to pursue this goal. The machining of experimental samples from previously in-service pipelines will be performed by NOVA. Researchers at Western University will characterize steel compositions and microstructures using the advanced surface analytical techniques available at Surface Science Western and in the Department of Earth Sciences. NOVA will then apply a stress load using a mechanical testing system while simultaneously monitoring the electrochemical conditions, on the pre-analyzed surface, in simulated groundwater. After chemical/mechanical exposure, researchers at Western will re-examine the pre-analyzed corroded surface to determine which microstructural properties are most susceptible to the initiation and growth of stress-induced cracks. Quantification of SCC degradation rates for different commercial steel microstructures will facilitate the development of the new alloy designs required for a safer energy pipeline infrastructure in Canada.