Just figured I would throw this out for discussion. I'm battling water/ condensation in under- bed toolboxes on flatbeds. The box can be clean and dry, with a good door seal. Close it up, come back 24-36 hours later and depending on humidity levels there can be water droplets clinging to the walls and small puddles in the bottom. It's bad enough that if I leave my toolbag in the box overnight, some of my tools develop light surface rust. We're having the same issue on a few of our other trucks.
The boxes are mounted by bolts through the top and one end with large plates inside to distribute the load. We've tried silicone/ RTV around the bolts and under the plates, with no noticeable changes. More ventilation might work, but the only way to get that is to leave the box open which isn't an option. Dessicant packs would work as well, but it seems like that would require a lot of dessicant and changing it often.
Anyone have a suggestion?