Just thought I'd point out that Golden Rods and other similar low power plug in devices are not dehumidifiers - they are heaters. They work to lower the relative humidity by raising the temperature some in the safe, and they also induce some air movement through the heat they add. The amount of water vapor in the air does not change, but raising the temperature is often enough to prevent condensation.
I use the small heaters in the winter as my safe is by an outside wall, and the air temp in it will drop below the temp in the house without one, but I also use desiccant bead packs that I dry out every so often too. Never had any signs of rust that way.