Small quantities of hydrogen present inside certain metallic materials make the latter brittle and susceptible to sub-critical crack growth under stress. Hydrogen embrittlement may occur as a side effect of electroplating processes.
Delayed failure is the fracture of a component under stress after an elapsed time, is a characteristic feature of hydrogen embrittlement (2). Hydrogen entry into the material may be effected during plating, pickling, phosphating, melting, casting or welding. Corrosion during service in moist environments generates hydrogen, part of which may enter the metal as atomic hydrogen (H) and cause embrittlement. Presence of a tensile stress, either inherent or externally applied, is necessary for metals to be damaged. As in the case of stress corrosion cracking, hydrogen embrittlement may also lead to a decrease in the threshold stress intensity factor for crack propagation or an increase in the sub-critical crack growth velocity of the material. The most visible effect of hydrogen in materials is a drastic reduction in ductility during tensile tests. It may increase, decrease or leave unaffected the yield strength of the material. 
Hydrogen may also cause serrated yielding in certain metals such as niobium, nickel and some steels (3).