How do you plate metal?
The key to plating metal is electrochemistry. Plating is electrodeposition. Connect the negative lead of a DC supply to the part to be plated, and connect the positive lead to an electrode in a tank of the plating solution. Stick your part in, turn on the juice, and wait for your results. The plating solution is basically a metal salt, and the metal in the metal salt is the one you're going to be plating onto your part. Yes, the part has to be super clean and free of any contaminants, but you knew that. Let's look at an example. Copper sulfate, which has CuSO4 as it's chemical formula, is in solution in the tank. The copper sulfate separates into Cu++ and SO4-- ions, which float around in solution. Your part is connected to the negative electrode. The power supply gives electrons to the copper ions that touch the part, the Cu++ ions we mentioned, and they become electrodeposited on the part as copper atoms. There are a number of different chemical compounds that can be used in electroplating. Our example was a sulfate. There are arsenides, carbonates and other chemical compounds available for use in electroplating that have the desired metal in them. Whether it's chromium, nickel, silver, gold or just about any other metal you can think of, you can plate it. Note that some precious metals are plated on with a sponge-tipped wand that is connected to a wire and then dipped in the electroplating solution. Gold is frequently plated on an object in this way because of the high cost of filling a tank with a solution of a gold salt. Wikipedia has more information, and a link is provided.