adam728 said:SOS pads, the ones with the soap in em.
A close second is steel wool, a decently fine grit.
3rd is Scotch Brite pads. If it's heavier rust it tears the pads up pretty quickly.
This is what I have found anyway when trying to clean rust off pipes, car wheels, and bicycle frames. I used to live in Michigan and I played with all my toys all winter long.