Hydrogen-induced delayed failure

Steigerwald EA, Schaller FW, Troiano AR. The role of stress in hydrogen induced delayed failure. Trans. Metall Soc. AIME, 1960 218 832-841. 

Effect of rare earths on hydrogen-induced delayed failure... 

This type of attack does not require any specific environment to take place, since it can take place simply in neutral or acidic wet environments. Failure due to hydrogen is named hydrogen embrittlement since it leads to a brittle-Uke fracture surface. Indeed, the ductility of the bulk metal does not change, but the propagation of the crack is due to the mechanical stresses induced in the lattice by hydrogen accumulated near the crack tip. If hydrogen is present in the metal lattice before the application of loads a delayed fracture may occur, i. e. the steel does not fail when the load is applied, but after a certain time. 

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