I have an older bike that's in the middle of being rebuilt and I need to take care of the chrome. The paint is still on the bike so I need to be careful of any chemical or physical processes that may discolor or destroy the finish. How can I best get that mirror finish back on my pitted lugs?
In the UK I've had success with Brasso, a cloth and lots and lots of elbow grease. Don't apply it with anything so harsh as wire wool or a scourer, just the impregnated wadding that comes with the product.
Unfortunately Brasso in the states is a slightly different composition so I can't vouch for it's efficacy.
I've read that using damp aluminum foil is the ticket. Check this out:
common way to clean a rusted chrome surface such as a fender is to use a fine steel wool. However, when you use this method you have to use a lot of elbow grease and you still end up with a slightly dull surface with some amount of scratching not to mention the messy 'dust' left over from the steel wool. That's because you are physically scraping off the rust.
When you use the aluminum foil method you are dissolving the rust chemically so you don't need to rub nearly as hard and since the aluminum foil is softer than the chrome, you are left with few if any scratches. This method also allows you to get the rust out of some minor pitting without having to dig into the surface.
Although I'm sure you could find a chrome-specific polish, you could try using polish for steel cookware (from the hardware store), baking soda and a damp cloth, or even tooth paste.
If there are more stubborn specs of rust, try a mild solvent and something more abrasive. In this case, try to stay away from the clearer areas because you'll leave a lot of small scratches that would need to be polished out later.
Rub it with some naval jelly and let it sit for a few minutes before attacking it with the steel wool. Wear rubber (not the thin ones, either) gloves when using this stuff. Follow the instructions on the package carefully. Naval jelly is a "Lock-tite" product. If my memory serves, it's active ingredient is phosphoric acid. Takes off rust like nothing else.