Titanium Alloys - Effect of Nitrogen and Ammonia on Titanium Alloys

Nitrogen and Titanium Alloys

Nitrogen reacts much more slowly with titanium than oxygen. Surface films formed above 540°C (1000°F) have a gold colour and with controlled processing are used to substantially enhance surface hardness and wear performance of titanium. Above 800°C (1400°C), excessive diffusion of titanium nitride may cause metal embrittlement.

Ammonia and Titanium Alloys

Titanium in not corroded by liquid anhydrous ammonia at room temperature. Low corrosion rates (0.13mm/year (0.0051 inch/year)) apply at 40°C. Moist or dry ammonia gas, or ammonium hydroxide (NH₄OH) solutions will not corrode titanium to their boiling point and above. Excellent resistance is offered by titanium to concentrated solutions of ammonium hydroxide (70%), up to the boiling point. Ammonium chloride scale formation may lead to under deposit corrosion of commercially pure titanium at boiling temperatures. Palladium containing alloys (ASTM Grades 7, 11, 16 and 17) and ASTM Grade 12 are totally resistant under these conditions.

Ammonia Steam and Titanium Alloys

At Temperatures above 150°C (300°F) ammonia will decompose forming hydrogen and nitrogen. Under these conditions there is the possibility of hydrogen absorption and embrittlement of the titanium. The high corrosion rate (11mm/year) experienced by titanium in an ammonia steam environment at 220°C (430°F) is believed to be associated with hydriding.

P Source: Titanium Information Group.

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