Put Dyna Bore Coat in the bore and Cerakote on the outside and there is no exposed metal to rust.
Dyna also makes an outside metal coating called Gun Shield. I asked Doug at Dyan if I could put Gun Shield on the outside of a still-in-the-white CM barrel that wouldn't get blued for a year or so (though it's not sitting in a humid area). Doug said if I put Gun Shield on the outside of the barrel the smith wouldn't be able to get it off to blue the metal. You could put Gun Shield on the barrel before Cerakote if you were worried.
The part about Cerakote being scratchable is true, though I have never had any trouble with Cerakote scratches. Blueing will scratch too, I've also not had problems with that. I tend not to drag my rifle across rocks, and the thickest briars I've hunted looking for rabbits didn't scratch the blueing on the shotgun.
