Eastwood industries has this zinc coating wash that you can soak your rotors in and it removes the rust and then zinc coats them. Make sure you paint them (non braking surface) or the rust comes back. I gave up an bought Baer rotors and they haven't rusted yet. I bought R1concepts rotors for my other car that are zinc plated and they have yet to rust either.
I painted my hubs and the infamous "rusty ring" with Rustoleum black Bar-B-Q over a year ago, and the are still perfect. I painted the calipers with Duplicolor red at the same time. This little project is fast, cheap and a very worthwhile improvement.
While I was waiting for my tires and wheels to be delivered I removed the calipers and masked and painted the rotors and hubs with rattle can black caliper paint. Time consuming at an hour+ per wheel but I don't have any rust showing now.
one of my brake rotors has a nice layer of rust on it, whats the best way to eliminate it, and keep it away?
Here's the thread on the DIY Eastwood process.
The pads will eventually wear the zinc off the firepath and it will rust, but the pads will clean it off with first application of brakes. The rest of the rotor, including down inside the vanes where the rust drips out or gets flung all over your wheels, won't rust anymore after the Eastwood treatment.