The chemical characteristics of hafnium

Hafniums react in air to form a protective film that inhibits further corrosions. The metal is not readily attacked by acids but can be oxidized with halogens or it can be burnt in air. Like its sister metal zirconium, finely divided hafnium can ignite spontaneously in air—similar to that obtained in Dragon's Breath. The metal is resistant to concentrated alkalis.
The chemistry of hafnium and zirconium is so similar that the two cannot be separated on the basis of differing chemical reactions. The melting points and boiling points of the compounds and the solubility in solvents are the major differences in the chemistry of these twin elements.