• Corrosion product films (FeCO 3 , Fe 2 O 3 , FeS) hinder hydrogen permeation into X80 steel. • Hydrogen barrier effectiveness increases in the order: FeCO 3 < Fe 2 O 3 < FeS. • FeS-covered steel reduce hydrogen embrittlement index from 45.0% (bare X80) to 12.5%. • Fracture mechanism shifts from HEDE to mixed HEDE/HELP mode with less H ingress. • 5.Corrosion film type dictates effective hydrogen concentration, which governs fracture mechanism transition. The safe transportation of hydrogen via natural gas pipelines is threatened by hydrogen embrittlement of high-strength steels, which is further affected by corrosion product films (CPFs) on the pipe inner wall. This work explored the effects of FeCO 3 , Fe 2 O 3 and FeS films on hydrogen permeation and embrittlement of X80 pipeline steel using experiments and first-principles calculations. All three films were n-type semiconductors and act as hydrogen barriers with different efficiencies. The hydrogen-blocking effect followed the order FeCO 3 < Fe 2 O 3 < FeS. The hydrogen embrittlement index droped from 45.0% (bare steel) to 12.5% (FeS-covered steel). As the effective hydrogen concentration in the steel decreases, the fracture mode changed from HEDE-dominated brittle fracture to a mixed HEDE/HELP mechanism. First-principles calculations revealed that hydrogen adsorption energies and diffusion barriers increased sequentially in the three films, explaining their enhanced hydrogen resistance. This study clarified the effects of corrosion product films on hydrogen behavior in X80 pipeline steel and provided a basis for the safety evaluation of hydrogen-blended pipelines.
Qin et al. (Wed,) studied this question.