Nothing to do with humidity levels but I have been using Fluid Film in the spray can the last few years for rust prevention in my shop and it works pretty well. Does not evaporate and hangs on for a long time.
I have several patents through work. Expensive and time consuming. Also expensive to defend when someone copies your idea..... and almost impossible to defend if the copy comes from China.
Not sure what you are doing with the car but another option is use roll bar padding instead of the alum. Might be a little easier on the knees and elbows.