Hydrogen embrittlement is the hydrogen-induced cracking of metals, particularly steel which results in degraded mechanical properties such as plasticity, ductility and fracture toughness at low temperature.
At 200 °C, hydrogen atoms can diffuse out of iron and partial stainless steel and is the minimum temperature needed for the process.
Zhou et al. show the comparison of stress-strain curves of the unannealed X80 pipeline steel and specimens that were annealed at 200 °C for 12 hr.
At 200 °C, carbon atoms have sufficient energy to diffuse into the interstitial sites of dislocations forming Cottrell atmosphere.
The type of lattice defects are related to the activation energy for release of the trapped hydrogen.