How does dehumidifier get the moisture it collects out of the safe 🤔.
If your safe is in an area with a consistent temp, then you probably don't need anything. I've had my safe for about 14yrs. I've never used a DH and I've never had a rust problem... and I don't coat my guns with oil. I would use a desiccant if I needed to remove moisture.
X2 the golden rod. Mine has been running for probably 20 years straight no issues. When I worked/lived in SW Louisiana I had a shotgun rust that I left in the corner next to the front door, Ac/heat all year, still rusted. The guns in the safe with the golden rod rust free. The rod just stays hot and drys the air inside the safe...no water to dump out.
I use Golden Rods and Eva Dry rechargeable ones in mine. Make sure you get the correct size rod for your container size. The Eva-Dry E333 is the most common one but the E-500 is a better choice if you can find it, again get the correct size for your container
I've got my safe sitting in my basement garage in easily one of the most humid areas of the state. I put some boards under it to allow air flow so the bottom of the safe wouldn't rust, and I put one of the bigger golden rods in there. Over 2 years now like that and not any rust issues at all.
Normally the bottom of the safe isn't finished and will rust pretty quick. You could use 1X4s or even treated deck boards next to the lag hole when you anchor it to create your air gap off the concrete.
I live in South West Georgia and humidity is always present. I have a cannon safe with one of the cylinders you can out in the oven in it. Once it changes colors you bake it for several hours. I dont have any problems with rust on my guns in the safe, but it is inside the house in the living room.