Gaseous hydrogen permeation of pipeline steels: A focused review

Hydrogen pipeline transportation, with the advantages of large capacity, low energy consumption and low cost, is the key to achieving large-scale transportation of hydrogen energy. Hydrogen embrittlement is a major safety challenge for hydrogen-exposed steels, which has been studied for years. However, up to 90 % of hydrogen embrittlement studies have been conducted in aqueous hydrogen environments. For hydrogen pipelines, gaseous hydrogen embrittlement caused by the transported gaseous hydrogen media should be paid more attention. The greatest difference between the two types of hydrogen embrittlement comes from the hydrogen permeation process. To advance the understanding and comprehension of gaseous hydrogen permeation, in this review, we report on the detailed process of gaseous hydrogen permeation, with a particular focus on the adsorption/absorption process and the difference between gaseous and aqueous hydrogen permeation. The experimental/ simulation methods and the corresponding results focused on gaseous hydrogen permeation are reviewed. Additionally, considering the difference between the laboratory testing environment and actual hydrogen pipelines, we analyze the existing research limitations in gaseous hydrogen permeation, focusing on four aspects: corrosion product films, gas components, flow condition and stress condition. The aim of this review is to provide technical support to reduce the risk of hydrogen embrittlement in hydrogen pipelines and accelerate the utilization of hydrogen energy.