Zirconium and
titanium have many similar physical and chemical properties. For example, their melting point is very high, pure titanium: 1668 ℃, pure zirconium: 1852 ℃.Zirconium and titanium have high chemical activity, and zirconium is higher than titanium, but the surface can form a dense passivation film, has a 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 equipment. Because of zircon zirconium and hafnium are symbiosis in the mine, zirconium ore content of hafnium in about 2% of the zirconium content - 3%, zirconium and hafnium all aspects of the physical and chemical properties are similar, from the zirconium and hafnium symbiosis of zirconium in the mine producing zirconium hafnium content less than 0.01% of the high cost, but also because of the chemical and physical properties of zirconium and hafnium are extremely close, thus producing chemical grade zirconium are not reduce the content of hafnium, zirconium content of hafnium in general not more than 4.5%.Although zirconium has the standard of nuclear energy grade zirconium material in China, there is no national standard or industry standard of chemical grade zirconium material (in preparation).
Zirconium is also a passivation metal, very easy and oxidation, forming a dense passivation film on the surface, zirconium material can withstand most organic acid, inorganic acid, strong alkali, molten salt, high temperature water and liquid metal corrosion. Hydrochloric acid of all concentrations below the boiling point of atmospheric pressure has excellent corrosion resistance, but hydrochloric acid above 149 ℃ has the possibility of hydrogenation. Zirconium can be used in nitric acid below 250 ℃ with a mass fraction of less than 70%, but it is easy to ignite in concentrated nitric acid with little water content. Zirconium in organic acid corrosion resistance, but in hydrofluoric acid, concentrated sulfuric acid, concentrated phosphoric acid, water, bromine, hydrobromic acid, fluorosilicic acid, calcium hypochlorite, fluoroboric acid corrosion resistance. Corrosion resistance is not found in oxidizing chlorides such as copper chloride and ferric chloride, but in reducing chlorides.
Zirconium in the air, 425 ℃ will be seriously peeling, 540 ℃ to generate white zirconia, more than 700 ℃ oxygen crisp. Zirconium reacts with nitrogen at above 400 ℃, and reacts strongly at about 800 ℃.Vacuum annealing does not remove oxygen and nitrogen from zirconium. Zirconium begins to absorb hydrogen above 300 ℃, producing hydrogen embrittlement, which can be removed by vacuum annealing at 1000 ℃.
