I have had no rust problems, BUT I live in west Texas where normally high humidity is 15%. This year however we have already more than doubled our annual rainfall, trypical humidity been around 45% and no problems. Don't think the liner will hold any more moisture unless you leave/have it out in the rain. Then if you do, just open it when you get in to air out. If it's in the rain without the liner, you probably need to open it to air out any way. Bottom line, if you are in an extremely humid area or in rain, air you boxes out if they get damp, with or without liner.