By Jean Broge, Manager, Content and Product Development at AMPP

Carbon capture, utilization, and storage (CCUS) was the focus of a Tuesday morning Research Topical Symposium (RTS) at the 2026 AMPP Conference. As carbon capture infrastructure expands, understanding how anthropogenic carbon dioxide (CO₂) streams affect pipeline materials is becoming increasingly important.  

A central technical challenge is defining acceptable impurity limits for transported CO₂ streams, since trace constituents such as hydrogen, water, sulfur compounds, or oxygen can significantly influence both fracture behavior and corrosion risk in pipeline steels. Unlike traditional CO₂ pipelines that transport relatively pure geologic CO₂, captured industrial streams — originating from sources such as ammonia plants, hydrogen production facilities, and steel manufacturing — may contain impurities that introduce new mechanical and corrosion risks for pipeline steels.

In the presentation “Effect of Dilute H₂ on Pipeline Seam Weld Integrity in CO₂ Pipelines,” Rick Noecker of ExxonMobil examined the effect of dilute hydrogen on seam weld integrity in dense-phase CO₂ service. As Noecker noted, “a little bit of hydrogen can go a long way.”  

Research has shown that hydrogen partial pressures as low as 1 bar under dense-phase (near-supercritical) CO₂ pipeline operating conditions can significantly reduce the fracture toughness of high-frequency electric resistance welded (HF-ERW) seam welds in modern line pipe steels — materials that have historically received close scrutiny in pipeline integrity programs — potentially lowering toughness to roughly one-third of the material’s in-air value.

Such reductions raise important concerns for integrity assessments, where resistance to running ductile fracture propagation must be maintained. Laboratory coupon testing has also indicated that dilute hydrogen may promote static crack growth in both vintage and modern pipeline steels. These findings highlight the importance of properly characterizing fracture toughness and crack-growth behavior when evaluating pipelines designed to transport anthropogenic CO₂ streams.

A second presentation, delivered by Yoon-Seok Choi of Ohio University, explored corrosion processes in dense-phase CO₂ environments and the challenges associated with obtaining reliable laboratory corrosion data.  

Dense-phase CO₂ corrosion studies often rely on complex experimental systems in which impurity injection methods, equilibration time, and experimental configuration can significantly influence results. Choi discussed improvements to batch autoclave testing methodologies designed to enhance experimental reliability and reproducibility.

Experimental results demonstrated that steel surfaces can act as catalytic sites for localized acid formation — even when thermodynamic models predict minimal acid generation—highlighting the importance of integrating surface reaction kinetics with bulk-phase CO₂ chemistry, particularly under conditions where trace water or impurity-driven reactions may promote acid formation at the steel surface.

Although the two presentations examined different degradation mechanisms — fracture behavior and corrosion chemistry — both highlighted how impurities present in anthropogenic CO₂ streams can significantly influence the long-term integrity of pipeline materials.

The presentations underscored the evolving materials challenges associated with transporting anthropogenic CO₂. As CCUS pipeline networks expand to support large-scale decarbonization efforts, improved materials characterization, experimental methodologies, and predictive models will play an increasingly important role in guiding pipeline design, integrity management, and safe long-term operations.