I have mine in the garage with an Evo-dry (plug in to recharge). I have far less trouble with moisture than I did when it was in a locked closet inside.
My dad has a safe in the garage (40 gun or so), bolted to the floor, I can't remember if wall also or not... Set on two 2x4's, and bolted through them, has a golden rod for humidity. Had the safe for... 10+ years? Never seen any rust on any of his guns, or mine that were stored there. Of course, we always clean right after shooting, and wipe down with silicone impregnated gun and reel cloth... Even wiping fingerprints and such where we held the gun putting it into the safe...
I have a Ft. Knox safe that has been in my garage for the past 4 years. There's one of the Remington plug in to recharge dehumidifiers thrown in by the long guns.
I recharge it every couple of weeks.
Never seen a spot of rust on any of my guns.
Never seen a spot of rust on any of my tools for that matter either, and they're just sitting on the shelf.
Garage is insulated, but not entirely sealed.
I had a small electric heater installed to keep it around 50 F during the winter.
Safe is bolted directly to the concrete floor.
I think it's more important to make sure that your gutters are adequately moving rain water away from your house than spending time/money on elaborate dehumidifying setups.
I agree with those who have expressed concern about someone jerking the safe out of the garage with chains. Think about where you're going to put it before you bolt it down.
I recall that the robbery that happened that way was done with a tow truck.
It seems to me to be extremely unlikely that a standard size safe full of guns/ammo/misc. could be lifted into a normal pickup truck by hand, even if there were ten guys there doing it.
Also seems unlikely that a normal pickup truck would be able to support the weight of a full safe that way either.
I have had mine in the garage for over 10 years after moving it to this house. It is bolted to the floor and has a golden rod. Garage is not climate controlled and I have not had any problems. I prefer it in the house but when we moved I didn't want the hassle of moving it up steps again.
Buddy of mine has a safe in a unheated garage and the only thing I've seen him do is give every gun that goes in a heavy coat of gun oil. Seems to work for him?
Seems to me having a gun safe in the garage would make getting to one's guns a colossal PITA, especially if you also use the garage for its intended purpose (parking cars) as opposed to a utility/storage room or man cave. I'm always moving stuff into and out of my safes; garage location would be a no-go for me.
Couple of yeras ago I bought a large "remmington " safe. The they told me it would be an extra 125.00 to move the 700 pound beast upstairs. I found a space in the corner of the garage and there it sits. It has a golden rod hooked up to it that is ona a clock. It works great. The garage is hooked up to ADT and you need a key and combination to get into it. It sits on a pallet off the ground.
My safe is about three feet away from my harley also. Thry a "golden rod" Some safes have places in the back that you can safely hook the rod in you safe. I set mine to run 5 - 6 hours a day. You have to adjust it for your needs. When I first got it I had an old shot gun with a rubber butt pad. In three months it was gone.
A cheaper solution to helping keep a safe dry is a simple light bulb. Even a 7-1/2 watt night light bulb makes enough heat to keep a normal safe dry (plus it makes it easier to see everything) Like another poster warned, some heat is good, too much heat will casue damage. It only takes about 5 degrees above ambient to keep the moisture out. Good Luck
I have my "toy vault" located in my garage and haven't had any moisture issues. The garage is heated and a/c'd and I just use one of those silica type coffee cans. After several years - no issues.
My safe has been in the garage now for around 10 years. It sits on a couple of treated boards with bolts running through them into concrete anchors in the floor. The garage is heated to above freezing in the winter and is fully insulated. I run a goldenrod and have never had a problem with rust. The floor in epoxy coated and the base of the safe is sealed with additional concrete to block a prybar. It is pushed up against a wall to prevent getting a chain around it.