For all you science minded people, since the rust (iron oxide) is less dense than the aluminum and the steel is more dense than the aluminum the aluminum takes off the rust without damaging the steel.

So get a cup of water and a rag, dip some aluminum foil in it, and rub away. It is like magic.

...

There are quite a few alternatives –- brass bristled brushes instead of steel. Like the aluminum foil, brass is softer than chrome or steel.- liquid or semi liquid products like Naval Jelly and Simichrome polish. Classic car restorers’supplies list many effective rust removers that won’t damage parts in their catalogs or web sites.- There are “rust erasers” available, big blocks of rubber, some with a mild abrasive in them, that will rub rust away. Pencil or ink erasers will work, too.After removing the rust you have exposed bare steel – if there is rust on chrome, then the chrome is cracked, chipped or pitted, exposing the steel underneath. Steel exposed to oxygen and water will re-rust quickly (Even a humid day will do it.). Protect it with at least a coat or two of paste wax or some other type of sealer.

Cool.

 the foil and water create a slurry of aluminum oxide (when you start rubbing you'll see a dark grey goo forming) and that along with the friction/grit of the foil will remove small amounts of pitting and surface rust, and also at the same time acts as a polish for the chrome all without scratching it like steel wool would do. I've also seen some people do it with cola rather than water, i found that only made things sticky and not much else.

via: http://www.accessnorton.com/cleaning-chrome-with-aluminum-foil-t13557.html

Soda is from Mythbusters, apparently: http://lifehacker.com/5383384/polish-chrome-with-aluminum-foil-and-cola

It is! I remember that episode. 

Electroplating: http://science.howstuffworks.com/electroplating-info.htm

Electroplating, the process of coating a metal object with a thin layer of another metal by means of electrolysis. The electroplated coating is usually no more than .002 inch (.05 mm) thick. Electro-forming is a similar process except that the thin layer is applied to a nonmetal that is later destroyed.

Electroplating is used to give metal objects a better appearance or to protect them from corrosion, wear, or rust.Tableware, trays, decorative pieces, and jewelry are plated with gold or silver to make them more attractive. Copper is coated with chromium to protect it from corrosion. For the same reason iron and steel are plated with nickel, chromium, tin, zinc, or cadmium