Localized Electrochemical Analysis of Weld Zone Corrosion in CO2-rich Environments

Carbon capture, utilization and storage (CCUS) efforts will play a critical role in the decarbonization of the global energy future. Readying infrastructure for the task becomes particularly prudent with the direct link to production of blue hydrogen for use as a utility fuel and energy storage mechanism. CO2 transportation infrastructure design and construction efforts are challenged by an accelerated timeline for expansion of CO2 networks, and integrity assurance, considering typical pipeline materials, will be challenged by the complex compositions being transported within the pipelines.

Material and environmental interactions are still not well understood in CO2 environments despite decades of research. This is especially true with bulk phase interactions of reactive impurities and propensity for dropping out of a secondary liquid phase. Aqueous phase separation in dense phase CO2 transportation is anticipated to be less like two phase flow and more like droplet condensation on the walls of pipeline infrastructure. Thus, the corrosion threat associated with the secondary phase will be localized in nature. This work examines a capability of conducting localized electrochemical parameter analysis in a single droplet via a bespoke syringe cell setup operatable in a CO2-rich environment. The initial focus of this work was to understand the discrete differences in resistance to carbonic acid corrosion across weld zones of pipe steel. The localized electrochemical cell was used to analyze instantaneous corrosion rate differences between pipe body, heat affected zone, and weld seam, as well as time to initiation with respect to varied amounts of applied stress. Future phases are to include the influence of impurities on the drop-out chemistry and subsequent effects on corrosion rate and corrosion mechanism.