Effects of surface oxide films on hydrogen permeation and susceptibility to embrittlement of X80 steel under hydrogen atmosphere

Hydrogen embrittlement (HE) induced by hydrogen permeation is a serious threat to the hydrogen transmission pipeline. In this study, oxide films were prepared on X80 steel by applying high-temperature oxidation, blackening treatment and passivation in concentrated H2SO4, and their effects on hydrogen permeation and HE susceptibility of X80 substrate were studied by conducting hydrogen permeation tests and slow strain rate tension (SSRT) tests. A numerical diffusion model was established to quantitatively determine the resistance of these oxide films to hydrogen permeation. Results showed that the oxide film prepared by high-temperature oxidation presented the highest resistance to hydrogen permeation with the ϕm/ϕf value of 3828, and the corresponding HE index decreased from 38.07% for bare X80 steel to only 4.00% for that covered with oxide film. The characteristic of the corresponding fracture surfaces changed from brittle features such as quasi cleavage facets and secondary cracks to typical ductile dimple feature.