Hafnium has been successfully alloyed with iron, titanium, niobium, tantalum, and other metals. Finely divided hafnium is pyrophoric and can ionite spontaneously in air. Care should be taken when machining the metal or when handling hot sponge hafnium. At 700 deg C hafnium rapidly absorbs hydrogen to form the composition HfH1.86. Hafnium is resistant to concentrated alkalis, but at elevated temperature 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 50,000 kg.