if you are talking a home you own, fix the problem...
not going argue geographic differences, but in southern MN heat & humidity is about as bad as it gets, during the summer... ( think 10,000 lakes steaming in the hot summer heat )
I used to have problems... ( my stuff is in the basement as well ) central air conditioning, & 2 large dehumidifiers, & I no longer have a problem... if the air is cool & dry in & around your safe, it will be cool & dry in your safe...
my local builder has several safes in his basement, & he has had many rifles in long term storage for many years now, with nothing but a normal wipe down with an oily rag before putting them away, & has never had a rust issue, running his central air, ducted to the basement, he doesn't even need a dehumidifier, & nothing like silica or golden rod in the safes... I used to oil more heavily, & the guns were OK, but my leather slings & such used to get scuzzy in the safes, with just one dehumidifier, & nothing like silica in the safes... I added 2 extra outlet vents to the heating & AC unit, one in my storage / loading area & a 2nd dehumidifier sitting in my gun safe / reloading area, & I've not had any problems for the last couple years...
IMO, you won't need anything in your safe, if the surrounding air is cool & dry
