The surface oxide film on titanium acts as an effective barrier to penetration by hydrogen. Disruption of the oxide film allows easy penetration by hydrogen. Absorption of several hundred ppm of hydrogen results in embrittlement and the possibility of cracking under conditions of stress.
Titanium can absorb hydrogen from environments containing hydrogen gas.
In the presence of pure hydrogen gas under anhydrous conditions, severe hydriding can be expected at elevated temperatures and pressures. This is shown by the data in Table 22 . These data also demonstrate that surface condition is important to hydrogen penetration. Titanium is not recommended for use in pure hydrogen because of the possibility of hydriding if the oxide film is broken. A more serious situation exists when cathodically impressed or galvanically induced currents generate nascent hydrogen directly on the surface of titanium.