From hydrogen ingress to failure in pipeline steels under electrochemical and gaseous environments: A review

Hydrogen is a promising energy carrier, but transporting it through high-strength pipelines raises concerns of hydrogen embrittlement. Ensuring the deployment of hydrogen-tolerant pipeline steels requires extensive materials testing and reliable qualification programs. To accelerate this process, electrochemical methods have been proposed as preliminary tools alongside gaseous testing. Although the ingress mechanisms that strongly influence hydrogen uptake differ fundamentally between aqueous and gaseous environments, diffusion and trapping, which dictate hydrogen permeation, remain similar in both environments. The susceptibility of steels to failure is strongly linked to diffusible hydrogen and its interactions with internal traps, making their understanding vital for predicting and mitigating hydrogen-induced degradation. This review provides an overview of the different stages of hydrogen in steels, advanced experimental techniques used to characterize hydrogen uptake and damage, hydrogen embrittlement mechanisms, and mitigation strategies. Emphasis is placed on comparing hydrogen uptake through different charging methods and consolidating key findings across environments.