The yellow zinc plated nuts & bolts under our TT started to rust after just one year. Our TT got delivered during a winter when there was lots of salt on the roads. Why can't dealers hose the underside down to remove road salt?? I replaced visible nuts & bolts on the elec. stab jacks with stainless steel. Still looks purdy after several seasons now. The plating they use (Chinese I assume) must be only only a couple of atom layers thick. :M Stainless steel isn't always stainless tho.
The frame and other painted things underneath is rusting in various spots. The powder coating layer they use also seems to be pretty thin (more like extremely thin). I also don't think they do a very good job of prepping the metal before powder coating. I need to get under the frame one of these days with some Rustoleum and do some touchup. Just can't get excited about the thought of working on my back over such a large area.