Im currently going through this. Ive got a shipping container workshop. I had a dessicant dehumidifier which worked well until about 2 weeks ago when it died.... i went in one day and the machines were wet and starting to rust! I looked on the internet which suggested covering the machines, so i did that first with a couple of old blankets ( rusted underneath them ) and then a waterproof cover ( still rusted )
I should add each time i cleaned them back and silicone sprayed. Also, the condensation on the roof was literally dripping.
I bought another dehumidifier ( bigger ebac ) but this time a refrigerant one, and it isnt as good as the dessicant, but i think this is also due to the cold weather, dessicant ones work down to about 5° and refrigerant ones are about 10°?
I am now putting insulation internally on the cieling. The container is on top of a hill and would never warm up if i put a little heater in there, plus i would be uneasy leaving one on all the time unattended.....
Im buying some machine wax after ive written this!!