Hydrogen uptake induced by CO2 enhances hydrogen embrittlement of iron in hydrogen blended natural gas

The hydrogen embrittlement behaviour of pure iron in different environments is investigated via fatigue crack growth tests, hydrogen permeation tests and first-principles calculations. The results show that the fatigue crack growth rate (FCGR) in H2 is much higher than that in N2. NG and CO2 further enhanced FCGR in an H2 environment. Hydrogen permeation tests show that both CO2 and NG can accelerate the diffusion of hydrogen in pure iron. This is mainly because CO2 can effectively reduce the diffusion activation energy of hydrogen atoms from the surface of pure iron to the subsurface.