Tinplate Coating.?

Question

What is the coating on tinplate?
What is the purpose of putting a coating on tinplate?
Plz help..for school assignment.

Answer 1

Tinplate
http://en.wikipedia.org/wiki/Tinplate
1.Tinplate is made by rolling iron or steel in a rolling mill, removing any scale (rust) by pickling it in acid and then coating it with a thin layer of tin.
2.Formerly, tinplate was used for cheap pots, pans and other holloware, but galvanised (zinc-coated) vessels are now used. Zinc protects iron electrolytically, that is, the zinc will dissolve to preserve the iron, whereas tin will only protect the iron if the tin-surface remains unbroken. This is why it is not safe to eat food from a rusty tin can.
..............Bonus Extra...................
http://en.wikipedia.org/wiki/Tinplate#History
The first production of tinplate was probably in Bohemia, from where the trade spread to Saxony, and was well-established there by the 1660s.

Answer 2

I would imagine it is to prevent rust, what exactly it is i'm not sure, probably some clear coat or form of paint.