Corrosion of steel pipelines continues to present major challenges to the oil and gas industry, with billions of dollars spent annually on technologies to mitigate corrosion-related losses. Despite the daunting fiscal impact, the processes that govern steel corrosion are still not well understood, due in part to the complex nanostructure of processed steel materials. Thermodynamic models have predicted that the nanoscale fluctuations in composition and structure that give steel its attractive macroscale properties may also create electrochemically active interfaces within the nanostructured steel, leading to accelerated material loss on the nanoscale via galvanic corrosion; however, resolution of such a dynamic, nanoscale process requires in situ investigation under liquid flow and with nanoscale resolution, and this instrumentation has only very recently been developed. This collaborative project seeks to tackle corrosion at its source by shedding light on the nanoscale features and processes involved in the initiation of corrosion in actual pipeline steel using a coupled ex situ / in situ liquid-cell transmission electron microscopy (LC-TEM) approach. The goal is the development of a mechanistic understanding of the advent of corrosion and the identification of the nanoscale features and compositional fluctuations implicit in rendering steel surfaces susceptible to degradation in wet environments. These key factors will ultimately inform the development of technologies to mitigate corrosion-related losses. To minimize the complexity inherent in the analysis of a real field material, extensive antemortem characterization was employed using a combination of electron diffraction techniques (EDS, PED, EELS, etc.). Samples were placed on a SiN window and exposed to a flow of aqueous CO2 using a microfluidic liquid-cell holder. Throughout the in situ exposure of the steel samples, images were acquired periodically to generate video sequences of nanoscale corrosion in real time. These in situ TEM results will be presented along with postmortem analysis and mirrored ex situ bulk-scale corrosion results in order to best capture the ways in which material nanostructure is predicted to affect the corrosion processes observed in larger size scale regimes.

Real-time, in situ observation of aqueous corrosion initiation in nanostructured steel

255th National Meeting (2018)

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