I lived near the great lakes for years, one of my cars, a 1993 beater had some serface rust, mind you that brand was not know for rusting to holes like our beloved toyotas... but I washed it once a week that took care of a lot of problems. undercoating your truck before and after winter works well. I have many friends still in ohio who rely on this and a good pressure washer/ auto car wash with underbody wash and it works.... the problem with auto washes is that they do not do a very good job, often that blast of water is only for a few seconds and is at the start of the wash.... then all the crap just runs down under your car again.... if you are willing to fight the good fight, yoour rust free fruck can stay just that.... mostly
good luck