Objective The substantial growth in global hydrogen energy demand has significantly increased the need for hydrogen transportation. Utilizing existing natural gas pipelines to transport hydrogen-doped blends is considered an economical and efficient option. However, this transportation process presents challenges, particularly the risk of stress corrosion cracking (SCC) in pipelines exposed to complex corrosive environments. This paper aims to provide a theoretical foundation and practical guidance for the safety assessment and protection of hydrogen-doped natural gas pipelines, based on a study focused on pipeline SCC behaviors under the combined effects of hydrogen, corrosion, and stress.

Methods The anodic dissolution mechanism underlying stress corrosion is elaborated, including processes such as oxide film cracking, slip dissolution, and corrosion-induced brittle fracture. The mechanism of hydrogen-induced cracking is discussed, along with an analysis that explores the influence patterns of various factors on pipeline SCC behaviors. These factors include material characteristics, such as element content, inclusions, and microstructure; environmental conditions, including temperature, applied potential, corrosive medium, and pH; stress factors, such as residual stress and corrosion-induced stress; and the effects of gaseous hydrogen.

Results The blending of hydrogen reduces the toughness of pipeline materials, significantly increasing the SCC risk. The microstructure, processing techniques, and mechanical properties of these materials are all linked to their hydrogen embrittlement sensitivity. An increase in carbon content contributes to greater brittleness, while the presence of grain boundary carbides acts as an accelerator the SCC process. Due to the inconsistent patterns in how varying temperature, applied potential, and corrosive media influence the SCC sensitivity of pipelines, a multi-factor coupling analysis based on different pipeline materials is deemed necessary. In terms of stress, both residual stress and membrane-induced stress significantly promote crack nucleation and propagation under the combined effects of hydrogen, corrosion, and stress, thereby accelerating the SCC process in pipelines.

Conclusion Research on the risk assessment and management related to SCC in hydrogen-doped natural gas pipelines is limited, particularly concerning the hydrogen blending ratio, safety, and related technological processes. Future research should focus primarily on core issues regarding pipeline transportation technology for hydrogen energy, including pipe compatibility, service life prediction, and the establishment and refinement of a technical standard system in this field, providing stronger safeguards for transporting hydrogen-doped blends through in-service natural gas pipelines and to facilitate the large-scale application of hydrogen energy.