OP. If the rust is till on the blade, i would try this: http://www.gunzilla.us/
Sprat it on, and let it sit fro 24 hours. Wipe it off, and see if it needs a second application. If it does, repeat step one, and after the second application spray some on the blade, and scrub it with a nylon bristle brush. If it will take rust off of a blued barrel without damaging the blueing, it should work on the coating on that blade.
Is it better to do the right thing for the wrong reason, or to do the wrong thing for the right reason? If you do the wrong thing for the right reason, is it still the wrong thing?
Si vis pacem para bellum.
There are two ways of doing something. Right and again.