I was watching MythBusters on SBS a couple of weeks back, and they used coke and then scrubed it with aluminium foil. Apparently coca-cola is real good for eating away rust and oxidisation. Not sure what the scrunched up alum foil dus. But anyway they reckoned it did a better job than most chrome cleaners. They also used it as a de-greaser with no success, but it did clean up any part that was rusty, battery terminals, ect. Good for cleaning coins too. Let it soak 2-3 mins and then scrub and wash off.
Never tried it myself but certainly is cheap.
ps Buy 2 litre bottle , that way if it don't work you can mix it with bundy and get pissed while thinking about your next plan of attack