[77newell]

I'm thinking that unless there is bare metal the probability of corrosion is not that much more than usual. My 77 coach (it's now 35 years old) was driven on salty roads several times and two summers ago I got underneath it and wire brushed the steel, both structural and sheet steel, primed it with a conversion primer (converts residual rust into an effective primer, and then coated with a waxy undercoating. While thin rust was prevalent there was no deep penetrating rust except in a couple of small places in sheet steel in the wheel wells.

The one caution I would suggest is to ensure that the plastic barrier is intact between the aluminum skin and steel structure below the floor line. With moisture and salt together with an absent barrier will rather quickly produce pin-holes in the skin.