Fracture strain in Inconel 625 decreases as hydrogen content charged by electrolysis increases, whereas that in SUS 316L does not change regardless of the hydrogen content of 161.5 mass ppm. Grain boundary fracture is observed on the surface of Inconel 625 absorbing a hydrogen content of 27.5 mass ppm, which corresponds to 59.2 MPa hydrogen gas at R.T using Sieverts law. In contrast, the fracture surfaces of SUS 316L hydrogen-charged at extremely high fugacities remain ductile dimples. Thus, hydrogen degradation susceptibility is much lower for SUS 316L than for Inconel 625
