I used the rust-mort product on a 92 Ranger I painted two years ago. I cut out and welded in new metal everywhere except above one of the front wheels. There was only a little surface rust so I wire wheeled it used rust mort then primed spot puttied and painted it. After a couple months the rust started again but it was 9 months before I had a chance to do anything about it. By then the rust was right through. It seemed like the rust had been accelerated. Next time I'll pass on the rust mort and just sandblast.
This brings to mind my old Dodge Dakota I need to repaint. I just purchased a 96 from Arizona to get the body panels from but was wondering what to do about the underside of the box and to prevent rust. POR-15 seems pretty expensive.
Doug