Page 30 - Curriculum Visions Dynamic Book

(Above) Zinc would react with the acidic contents of many cans. So,
tin plating is used as skin to protect the iron that goes into making up most of a “tin” can. However, if you scratch the surface tin plating on a tin can, the iron below will soon rust if exposed to air and moisture.
(Below) A common decorative protective coating is chromium. Here it is plated over a bathroom faucet.
Another, more durable way to protect things is to plate the surface of the metal with another metal that does not corrode. That is the purpose of tin plating on steel cans. Zinc is also plated onto steel to make galvanized steel, for example, in barbed wire.
Nickel and chromium are other noncorroding (almost inert) metals that are plated over other metals. They also have the advantage of producing an attractive, shiny silvery surface.
Faucets and many other household items are chromium plated. Chromium does not stick easily to steel, so a plating of copper and nickel has first to be applied to the steel, and then the chromium is plated onto the copper. All plating is done using a bath of liquid through which an electric current passes.
Galvanic protection
The term “galvanic protection” comes from Luigi Galvani, a famous Italian scientist who investigated electricity in the 18th century. Zinc is often plated on to steel, and in this form it is called galvanized steel. If a chip is made in the zinc exposing the iron, the zinc, the iron, and the water act as a battery. The zinc will lose electrons even more readily than iron, and so the zinc corrodes, leaving the iron untouched.
Cadmium and aluminium are other metals used for galvanic and oxide protection. The steel of exhaust
systems is commonly aluminium plated.
Plating
Zinc-plated steel screws can be used outside with confidence.
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