Magnesium(鎂)

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Magnesium
Magnesium is a fairly strong, silvery-white, light-weight metal that
slightly tarnishes when exposed to air. It is difficult to ignite(點燃) in 
bulk(大批), though it is easy to light if it is shaved in to thin strips.

The advantage of magnesium
1.It is hard, brittle and light (one third lighter than aluminum)
2.It is a reactive metal, can be prevent other less reactive metal from corrosion,
it is called sacrificial protection. 

The disadvantage of magnesium
1.The finished parts make up with magnesium must be protected against atmospheric 
attack through a special surface treatment that is called chromatisation. 
2.magnesium and its alloys, which fall within the designation electron, easily catch
fire on machining. Such a fire cannot be extinguished with water since water is 
decomposed by magnesium during hydrogen gas formation.

The use of magnesium
Magnesium are used mainly as refractory material in furnace(熔爐) linings(內層) for 
producing iron and steel, nonferrous metals, glass, and cement(接合劑).