Hafnium has been successfully alloyed with iron, titanium, niobium, tantalum, and other metals. Finely divided hafnium is phosphoric and can ignite spontaneously in air. Care should be taken when machining the metal or when handling hot sponge hafnium. At 700C hafnium rapidly absorbs hydrogen to form the composition HfH1.86. Hafnium is resistant to concentrated alkalis, but at elevated temperatures reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon.
Halogens react directly to form tetrahalides.
The yearly demand for hafnium in the U.S. is now in excess of 100,000 lb.