I recall that either Brownells or Cabellas sells a rifles torage bage that includes the use of a VCI (corrosion inhibitor) in the bag. I've seen amazing things with the use of these products - my father in law stored 3 classic pistols in a sealed box with some VCI and some silica gel - he left it sit in his garage in HOUSTON for 25 years, until my wife and I moved down here. I was there when he opened the box. I was STUNNED to see the guns were in pristine condition.
Corrosion can only occur if it has metal to eat, water to drink in the form of humidity, and oxygen to breath. If you can eliminate any of those factors and there will be no corrosion. Midsouth Shooters Supply sells pretreated VCI, as does a lot of other gun supply stores.
My gun safe has no humidity rod (too much heat and there are things in there - like gunpowder and primers - that don't want to be hot) I have a BIG box of silica gel (enough to control humidity in a 15x15 foot room), as well as a significant amount of VCI in the form of pretreatede cardboad and VCI paper. VCI acts to displace oxygen around the firearm with a non-corrosive contributing inert gas (I don't know how - but have seen teh same explanation at several different VCI manufactureing sites).
I suggest you follow that lead, combination of VCI storage bag, silica gel and clean and coat the firearm with a good gun lubricant.