A study on hydrogen uptake and diffusion in X65 pipeline steel using gaseous and electrochemical methods

Hydrogen, a clean energy carrier, is recognized as a critical building block to develop a carbon-neutral energy sector. To realize the hydrogen economy, it is essential to develop a hydrogen distribution infrastructure. Repurposing existing natural gas pipelines for H2 gas transportation is an economically favored choice for long-distance hydrogen transportation. However, pipeline steels can be subjected to hydrogen embrittlement (HE), and HE susceptibility is an essential part of evaluating the feasibility of repurposing pipelines. Hydrogen uptake and diffusivity can affect the degree of HE. H2 gas charging is challenging due to safety risks and limited testing facilities. In contrast, electrochemical charging is a safer and more accessible method. The objective of this PhD work is to relate electrochemical and gaseous hydrogen charging based on the hydrogen uptake. If the relationship is transferable to mechanical testing, electrochemical charging could support the evaluation of pipeline steels for H2 gas transport. Hydrogen uptake, diffusivity, and trapping in one vintage and two modern X65 pipeline steels were investigated. Both electrochemical and gaseous hydrogen charging have been conducted. Hydrogen desorption and permeation techniques were employed in the investigation.