OXYGEN
Titanium has excellent resistance to gaseous oxygen and air at temperatures up to about 700 degrees F (371 degrees C). At 700 degrees F it acquires a light straw color. Further heating to 800 degrees F (426 degrees C) in air may result in a heavy oxide layer because of increased diffusion of oxygen through the titanium lattice. Above 1,200 degrees F (649 degrees C), titanium lacks oxidation resistance and will become brittle. Scale forms rapidly at 1,700 degrees F (927 degrees C).

Titanium resists atmospheric corrosion. Twenty year ambient temperature tests produced a maximum corrosion rate of 0.0010 mpy (2.54 x 10^-5 mm/y) in a marine atmosphere and a similar rate in industrial and rural atmospheres.^(34)

Caution should be exercised in using titanium in high oxygen atmospheres. Under some conditions, it may ignite and burn. J.D. Jackson and Associates reported that ignition cannot be induced even at very high pressure when the oxygen content of the environment was less than 35%.^(35) However, once the reaction has started, it will propagate in atmospheres with much lower oxygen levels than are needed to start it. Steam as a diluent allowed the reaction to proceed at even lower O2 levels. The temperature, oxygen pressure, and concentration limits under which ignition and propagation occur are shown in figures 13 and 14. When a fresh titanium surface is exposed to an oxygen atmosphere, it oxidizes rapidly and exothermically. Rate of oxidation depends on O2 pressure and concentration. When the rate is high enough so that heat is given off faster than it can be conducted away, the surface may begin to melt. The reaction becomes self-sustaining because, above the melting point, the oxides diffuse rapidly into the titanium interior, allowing highly reactive fresh molten titanium to react at the surface.