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The most noted chemical property of titanium is its excellent resistance to corrosion; it is almost as resistant as platinum, capable of withstanding attack by acids, moist chlorine in water but is soluble in concentrated acids.
While the following Pourbaix diagram shows that titanium is thermodynamically a very reactive metal, it is slow to react with water and air.
The Pourbaix diagram for titanium in pure water, perchloric acid or sodium hydroxide
This metal forms a passive and protective oxide coating (leading to increased corrosion-resistance) when exposed to elevated temperatures in air, but at room temperatures it resists tarnishing.When it first forms, this protective layer is only 1–2 nm thick but continues to slowly grow; reaching a thickness of 25 nm in four years.
Titanium burns in air when heated to 1,200 °C (2,190 °F) and in pure oxygen when heated to 610 °C (1,130 °F) or higher, forming titanium dioxide. As a result, the metal cannot be melted in open air as it burns before the melting point is reached, so melting is only possible in an inert atmosphere or in a vacuum. It is also one of the few elements that burns in pure nitrogen gas (it burns at 800 °C or 1,472 °F and forms titanium nitride, which causes embrittlement). Titanium is resistant to dilute sulfuric acid and hydrochloric acid, along with chlorine gas, chloride solutions, and most organic acids. It is paramagnetic (weakly attracted to magnets) and has fairly low electrical and thermal conductivity.
Experiments have shown that natural titanium becomes radioactive after it is bombarded with deuterons, emitting mainly positrons and hard gamma rays.When it is red hot the metal combines with oxygen, and when it reaches 550 °C (1,022 °F) it combines with chlorine. It also reacts with the other halogens and absorbs hydrogen.
Source : http://en.wikipedia.org/wiki/Titanium |
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