Zirconium and titanium have many similar physical and chemical properties. For example, they have very high melting points: 1668℃ for pure titanium and 1852℃ for pure zirconium. Zirconium and titanium have higher chemical activity, zirconium is higher than titanium, but the surface can form a dense passivation film, has high corrosion resistance. Zirconium has better corrosion resistance than titanium in most highly corrosive media, which is why zirconium is more expensive than titanium, but it is still used in many chemical devices. Because zirconium is a symbiont of zirconium and hydrogen in mines, the content of zirconium in zirconium ores is about 2%≤3% of the content of zirconium, and the physical and chemical properties of zirconium are similar to ores. From the symbiosis of zirconium and hydrogen, the cost of producing hydrogen zirconium is less than 0. As the chemical properties and physical properties of zirconium are close to hafnium, the content of chemical grade zirconium is reduced. Zirconium content generally does not exceed 4.5% Chinese zirconium has nuclear grade zirconium standard, but there is no chemical grade zirconium Chinese standard or industrial standard.
Zirconium is also a passivated metal that oxidizes easily and forms a dense passivated film on its surface. Zirconium material can withstand most organic acid, inorganic acid, strong base, molten salt, high temperature water and liquid metal corrosion. Under normal pressure, hydrochloric acid has good corrosion resistance below boiling temperature, but hydrogenation reaction in hydrochloric acid can reach 149℃. Zirconium can be used in nitric acid below 250°C, with less than 70% by mass, but is susceptible to fire in concentrated nitric acid with lower water content. Zirconium is corrosion resistant in organic acids, but not in hydrofluoric acid, concentrated sulfuric acid, concentrated phosphate, water, bromic water, hydrobromic acid, fluorosilicic acid, calcium hypochlorite and fluoroboric acid. Corrosion resistance is not found in oxidized chlorides (e.g., copper chloride and ferric chloride) and is not found in reduced chlorides.
When zirconium is in air, it will be severely spalling at 425℃, white zirconia will be produced at 540℃, and oxygen embrittlement will occur above 700℃. Zirconium reacts with nitrogen above 400℃ and strongly at about 800℃. Oxygen and nitrogen cannot be removed from zirconium by vacuum annealing. Zirconium begins to absorb hydrogen above 300℃, leading to hydrogen embrittlement, which can be eliminated by vacuum annealing at 1000℃.
