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Tin has been known since ancient times. The old testament cites
tin as one of the known metals of the time (i.e. the others are gold,
silver, copper, iron,
and lead. In the 17th century, tin was quite popular for
use in tools and utensil. Since the end of the Bronze
Age, tin has been a plating medium for iron. A thin layer of tin prevents
the oxidation that would otherwise corrode
away iron objects.
Pure tin is ductile and malleable. It can be rolled, spinned and extruded.
It is silvery-white and looks much like aluminum, but feel
more like lead. Tin is found naturally in deposits of cassiterite
as stannic oxide, SnO2. The largest deposits are in Malaysia which
produces about one-third of the world's output. Bolivia, Thailand and Russia
produce about 40%. Only a small amount is mined in Canada.
Tin is best known for its use in the manufacture of tin cans. It is most commonly
seen as the outer layer on tin-plate or tin cans. It does not tarnish in the
air, and protects iron only by excluding oxygen from the
iron. This is in contrast to galvanizing
where the protection by zinc is due to its higher activity
than iron. Since tin is an expensive metal and tin is usually recovered from
scrap tin-plate.
Tin is a popular alloying agent used in the manufacture
of solders for electronic components. Soft solder is an alloy of lead and tin
containing about 50-70% lead and 30-50% tin. Depending on the composition of
the solder, it melts in the range of 183-250oC. Pure lead melts at
327oC and pure tin at 232oC.
Bronze that contains tin is very
resistant to corrosion and is similarly used for castings, especially for marine
propellers and other ship fittings. Bronze is also used for large statues and
bells.
Other useful tin compounds include: