Zrconium is stable in air at room temperature in its dense state, but its powder, shavings, or flakes are highly flammable. It can spontaneously combust above 200°C or burn violently upon contact with an open flame, emitting a bright white light and forming zirconium oxide (ZrO₂). It can continue to burn in carbon dioxide or nitrogen; fine zirconium powder may even spontaneously combust or explode.
Ignition Point: Dense zirconium only shows significant oxidation and combustion above approximately 1852°C (melting point), but zirconium powder can ignite at approximately 200°C. It is highly susceptible to combustion and even explosion upon contact with heat, friction, sparks, or oxidizers.
Combustion Characteristics: It releases strong light and high temperatures (up to 1500–2000°C) during combustion. The main product is ZrO₂ (white, irritating smoke). It is insoluble in water and should not be extinguished with water (as this may exacerbate the reaction). Dry sand, Class D metal extinguishing agents, or carbon dioxide are suitable extinguishing agents.
