What Are The Technical Parameters Of Zirconium?

Zirconium and titanium share many similar physical and chemical properties. For example, they both have high melting points: pure titanium: 1668°C, pure zirconium: 1852°C. Both zirconium and titanium are highly chemically active, with zirconium being more active than titanium. However, both form a dense passive film on their surfaces, resulting in excellent corrosion resistance. In most highly corrosive media, zirconium exhibits better corrosion resistance than titanium. This is why, despite being more expensive than titanium, zirconium is still used in many chemical equipment.

Because zirconium and hafnium often coexist in zirconium ore, with the hafnium content in zirconium ore being approximately 2%-3% of the zirconium content, and the physical and chemical properties of zirconium and hafnium being similar across the board, it is costly to produce zirconium with a hafnium content below 0.01% from zirconium-hafnium coexisting zirconium ore. However, because the physical and chemical properties of zirconium and hafnium are so similar, it is not necessary to reduce the hafnium content in the production of chemical-grade zirconium; generally, the hafnium content in zirconium should not exceed 4.5%.

Zirconium is also a passive metal and readily reacts with oxygen, forming a dense passive film on its surface. This makes zirconium resistant to corrosion by most organic and inorganic acids, strong bases, molten salts, hot water, and liquid metals. It exhibits excellent corrosion resistance in hydrochloric acid at all concentrations below its boiling point at atmospheric pressure, but may undergo hydrogenation in hydrochloric acid above 149°C. Zirconium can be used in nitric acid with a mass fraction of no more than 70% at temperatures below 250°C, but it is prone to pyrolysis in concentrated nitric acid with a low water content.

Zirconium is corrosion-resistant in organic acids, but not in hydrofluoric acid, concentrated sulfuric acid, concentrated phosphoric acid, aqua regia, bromine water, hydrobromic acid, fluosilicic acid, calcium hypochlorite, and fluoboric acid. It is not corrosion-resistant in oxidizing chloride solutions such as copper chloride and ferric chloride, but it is corrosion-resistant in reducing chloride solutions.

When exposed to air, zirconium will severely scale at 425°C, forming white zirconium oxide at 540°C. Above 700°C, it absorbs oxygen and becomes brittle. Zirconium reacts with nitrogen above 400°C, with the reaction becoming more intense around 800°C. Vacuum annealing cannot remove oxygen and nitrogen from zirconium. Zirconium begins to absorb hydrogen above 300°C, causing hydrogen embrittlement. This can be eliminated through vacuum annealing at 1000°C.