Grizzly, The humidity itself would probably takes months!??
I grease the inside and degrease the outside of the barrel with a solvent, plug the holes and apply Wahkon Bay (cold)Browning regent a couple times a day. It takes a few applications for it to start rusting all over. I take it out and rub it down with a clean rag to take off the loose stuff, re-apply browning and put it back in the box. Repeat, repeat, repeat. It takes several days to a week to get a deep brown that has a rough surface like about 240~360 sandpaper. You can use wet steel wool to smooth it out as desired, if desired. I like it ruff! Now, you MUST neutralize the acid, and I use a strong solution of Baking Soda and hot water. Rub it on thick like a paste and let it dry and set an hour, wash it off and do it again a little thinner this time. Wash, dry and OIL well. You'll need to oil it daily for a while to keep the rust from growing back if it wasn't neutralized well enough. There are a number of neutralizing agents in use, like anmonia, acetone?, etc. but this is what I've used for years and am comfortable with the results. This is just one of many variations on how to.... Works for me, nuff said. :front: