Use of existing steel pipeline infrastructure for gaseous hydrogen storage and transport: A review of factors affecting hydrogen induced degradation

The transition of the existing natural gas grid infrastructures towards transport and storage of hydrogen gas plays a prominent role in the global decarbonization of the energy landscape. Hydrogen absorption into pipeline steels may lead to a ductility decrease, particularly in the presence of stress concentrations. Hydrogen lowers the fracture resistance of steels, which may render them to become susceptible to crack extension under static loading. Furthermore, due to fluctuations in gas pressure and applied loads on the pipeline structure, hydrogen assisted fatigue crack growth could take place (even at relatively low hydrogen gas partial pressures). Therefore, the use of existing pipeline systems (initially not designed) for pressurized gaseous hydrogen transport requires prior confirmation of their fitness-for-service. Mechanical (load level and cycle frequency), material (microstructure, chemical composition and the presence of welds), and environmental variables (gas pressure, gas composition and temperature) influence the severity of hydrogen embrittlement by gaseous hydrogen. Investigations have indicated that the take-up of hydrogen by pipeline steel may be mitigated by the addition of gas impurities, i.e. inhibitors, to the gas mixture. The current work presents a literature overview of the relevant aspects in this consideration, indicating ample scope for further research in all abovementioned aspects.