So I have these waterproof tool boxes from Bostitch, nothing fancy. It appears condensation is building up in the boxes and causing spot rusting on some of my tools. I started putting a fine coat of wd40 on them to maintain, but I'd like to prevent the condensation from building up to begin with. Moving them into the house is not an option. I've read you can put some charcoal in your tool box. Perhaps even s sock of baking soda? How do you manage? Sure I'm not the only one with this problem.
It happens to me as well. Even my toolbox that I use every day at work. I would say that a light coat of oil would be your best bet, like you've been doing. I can't think of anything better.
Some people use those silica packs you get in electronics and such.
That's what I use. Whenever I unpack something that has these silica desiccant packs in it I save the packs in a large zip lock bag, that way if I need a pack I have em ready to use.
fill a couple old socks with simple white rice or dry Tapioca (ask the wife...)....and toss them in. just make sure the box is closed, and you don't have mice.....
Depending what kind of tools you use, I use spray on Turtle wax car wax. I did that when I did telephone and data work. In those cases your tools may get wet but you do not want to leave oily fingerprints on peoples walls, cabiness and furniture. Most of my ammo reloading tools, dies and equipment is raw steel. I spray the stuff down with car wax every so often. It heeps everything from getting that rusty coating and there is no oil to contamninate anything. Good Luck