Electrochemistry and pitting corrosion of nano-scale metallurgical features in pipeline steels

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The objective of the proposed research is to study electrochemistry and pitting corrosion of various metallurgical features in low- and high-strength pipeline steels, i.e., X65 and X100 steels, and correlate pitting corrosion phenomenon with the steel metallurgy at the nano-meter and atomic length scales.***    Development of high-strength steel pipelines has enabled significant economic benefits in oil/gas transmission. High-strength steels, such as X100 steel, feature a unique metallurgical microstructure, compared with low grade steels, such as X65 steel, to achieve a good combination of strength, toughness and weldability. This typically includes fine, sub-micron structures, which are usually at tens and hundreds of nano-meter scale.***    Pitting corrosion has been identified as one of the dominant mechanisms for the development of pipeline leaks. Initiation of pitting corrosion depends strongly on the metallurgical features of the steel. The unique metallurgical feature of high-strength steels is expected to affect pitting corrosion of pipelines. To date, research into the effect of steel metallurgy on pipeline pitting corrosion has remained macroscopic and statistical. The mechanistic information as to the exact initiation and growth of corrosion pits in steels has not yet been realized.***    In this research, an electrochemical atomic force microscope, combined with other surface and electrochemical techniques, will be used to simultaneously measure local electrochemical corrosion reactions, and characterize three-dimensional structure/ morphology of metallurgical features in pipeline steels with nano-scale spatial resolution in controlled environments. Specifically, this research will advance our understanding of the nano-scale metallurgical features in X65 and X100 steels, measure electrochemical behavior of the nano-scale constituents in these steels; and monitor pit initiation and growth to establish the correlation of pitting corrosion with steel metallurgy.***    Pipelines are a critical nation-wide network for oil/gas transportation. Ensuring safe pipeline operation is critical for the long-term health of an industry that has great significance to the Canadian economy. The research findings would contribute significantly to improving steels and pipeline integrity, which will be an important cornerstone in alleviating public concerns of safety, environmental impact, and reliability of pipelines. Moreover, the research will contribute to development of metallurgical nano-electrochemistry as a concept and approach for pipeline corrosion research. It is also anticipated that this pioneering research, which integrates electrochemistry, metallurgy and advanced surface analysis techniques, will establish a new methodology and strong scientific baseline for the understanding of mechanisms of pipeline corrosion.**