We have all seen chromium-plated auto-mobile bumpers, gold plated watches, and silver-plated spoons. Many other familiar things are given metal coating to make them look more attractive and to protect them from rust. These objects are usually made of steel, which is strong and cheap, and covered thinly with the other metal.

Other common way of coating an object with metal is called electroplating. An electric current is used to put the metal coating on the object and make it stick there.

To plate a spoon with silver, for example, the spoon is placed in a chemical solution that contains silver. The spoon is attached to the cathode, or negative terminal, of some source of electric current. A solid bar of silver id connected to the anode, or positive terminal, of the same electric circuit. An electric current is them passed through the spoon, the silver bar, and...