Here is a before of my new "used" rotor......

here is the after....and installed rotor.....

this little $3 jar plus a small amount of elbow grease and emory cloth did the trick....

found it at home depot.

Naval Jelly aka Ospho aka phosphoric acid, is pretty much the oldest rust remover/convertor out there. Quite effective. However, you still need to seal most surfaces (not brake rotors) to prevent new rust from forming.

Trekkor is a big Naval Jelly advocate.

I popped some fuzz out of my navel once but never jelly

Mike D.