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Why are some metals chromium plated?
Some metals are chromium-plated to make them look attractive and to prevent them from corroding or rusting.
Chromium is a silver-white, hard, brittle metal which was discovered in 1798 by N. L. Vauquelin. Its non-corrosive, high-strength, heat-resistant characteristics are utilized in alloys and as an electroplated coating.
In electroplating, the article to be plated is connected to the negative terminal of a battery and placed in a solution known as electrolyte. Direct electric current is introduced through the anode or positive terminal, which usually consists of the metal with which the article is to be coated.
Metal slowly leaves the anode and forms a deposit on the article. The electrolyte for chromium contains chromic acid and sulphuric acid. It deposits a bright top layer but this is not the only important part of the electroplating. The chromium is only about 0.00002 inches thick.
Under it lays a thick layer of nickel and beneath that again may be a layer of copper. Many household appliances are chromium-plated and so are the bright parts of an automobile. Tools, chemical equipment, electric appliances, gears, packing machinery, and hundreds of other articles are similarly treated to give them brightness, beauty or resistance to wear and rust.
Electroplated and polished chromium is bright bluish-white with a reflecting power which is 77 percent that of silver.