Rust naturally develops on metal when it comes into contact with oxygen and moisture; this natural oxidation will continue to grow if you don't remove it. When rust appears it will actually weaken the metal; if rust is growing on your rebar, clean the rust off as soon as possible to prevent it from weakening the rebar and whatever it is attached to. This will also prevent water from running over the rust on the rebar and causing a rusty water stain on surfaces in or around your home.
Put on gloves and goggles to protect your hands and eyes from shards of rust.
Scrub the rust stain with a wire brush. Work until you remove all of the rust from the rebar or until you remove as much of it as possible.
Scrub the rust stain with steel wool. Work the steel wool into the crevices of the wrapped rebar until all of the rust is gone.
Rinse the rebar with clean water to remove any rusty residue and dry it completely with a clean cloth.