Oxygen(O2) and Air
Titanium has excellent resistance to gaseous oxygen and air at temperatures up to 370°C. Above this temperature and below 450°C, titanium may form colored surface oxide films which may thicken slowly with time.

Above 545°C or so, titanium alloys lack long-term oxidation resistance and will become brittle due to the increased diffusion of oxygen into the metal.

Titanium alloys are totally resistant to all forms of atmospheric corrosion regardless of pollutants present in either marine, rural or industrial locations.

Hydrogen(H2)
The surface oxide film on titanium acts as a highly effective barrier to hydrogen penetration which can only occur when this protective film is disrupted mechanically or broken-down chemically or electro-chemically.

The presence of moisture effectively maintains the oxide film inhibiting hydrogen absorption up to fairly high temperatures and pressures. On the other hand, pure, anhydrous hydrogen exposures should be avoided particularly as pressures and/or temperatures increase.

Excessive absorption of hydrogen in titanium alloys leads to embrittlement if a significant quantity of the brittle titanium hydride phase precipitates in the metal. Generally, hydrogen contents of at least several hundred ppm are required to observe significant embrittlement.

The few cases of hydrogen embrittlement of titanium observed in industrial service have generally been limited to situations involving high temperature, highly alkaline media; titanium coupled to active steel in hot aqueous sulfide streams; and where titanium has experienced severe very prolonged cathodic charging in seawater.

Nitrogen(N2) and Ammonia(NH3)
Nitrogen reacts much more slowly with titanium than oxygen. However, above 800°C, excessive diffusion of the nitride may cause metal embrittlement.

Titanium is not corroded by liquid anhydrous ammonia at ambient temperatures. Moist or dry ammonia gas, or ammonia-water (NH40H) solutions will not corrode titanium to their boiling point and above.

Sulfur-Bearing Gases
Titanium is highly corrosion resistant to sulfur-bearing gases, resisting sulfide stress corrosion cracking and sulfidation at typical operating temperatures.

Sulfur dioxide(SO2) and hydrogen sulfide (H2S), either wet or dry, have no effect on titanium. Extremely good performance can be expected in sulfurous acid even at the boiling point. Field exposures in FGD scrubber systems of coal-fired power plants have similarly indicated outstanding performance of titanium.

Wet sulfur trioxide (S03) environments may be a problem for titanium in cases where pure strong, uninhibited sulfuric acid solutions may form, leading to metal attack. In these situations, the background chemistry of the process environment is critical for successful use of titanium.