Contrary to what some posters have stated, blueing does offer pretty good rust protection so long as you don't expose it to salt water and wipe your greasy (salty)prints off after handling it.
So basically no real corrosion protection.
I have never read, never been taught, and never have experienced bluing as a good corrosion inhibiter. If something has changed in the past hundred years please educate me but even professional hot bluing does not offer much in the way of corrosion protection. A freshly blued gun that is taken out of the final rinse tank and left exposed to the air will rust about as fast as bare metal, typically the gun is coated in oil and wrapped at least overnight. Bluing is basically coloring the metal, it offers possibly ever so slightly some corrosion protection but to no real degree, it is a finish for appearance.
Some people feel that the “high gloss” bluing offers better protection, this may or may not be true but the high gloss is not a result of bluing; you are looking at colored metal. IF the metal is polished and glossy before bluing, than it will appear as a high gloss blue, if rough like after bead blasting and you blue the metal it will be a matte appearance.
On that note you can keep bare metal from corrosion if you care for it. I know many who had the bolt bent on their mausers so a scope could be mounted, they left the bolt bare metal, it doesn’t rust easily, just wipe it down with a little oil once a month when not in use, same as a blued rifle especially but really for any rifle.