sand paper
BRAKING.
About all you can do is wire brush, and regularly apply heat resistant paint.
Best plan is ignore the rust. It's a no- win situation.
Rust on the brake rotor friction surfaces will wear off in short order. Rust on the rest of the rotor will stay forever unless you sandblast and paint (with high temperature paint).
sand paper.
I have rust on my brake rotors and it's not going away from breaking. I have it on all four wheels and it's ugly. How can I clean it off ???