I had the exact same thing happen to my 597. I removed the bluing from the barrel and sanded the rust pits out with sand paper, final sanded it and re-blued it with Birchwood Casey Perma-Blue. Can't tell it was ever rusted, but the bluing on the barrel is considerably nicer looking that the "painted" receiver.
NRA Lifetime Member Since 1999
"I ask, sir, what is the militia? It is the whole people except for a few public officials." George Mason