I have used lots of POR-15,and had good results.I have noticed that,like it says on the label,it is made to Paint Over Rust (hence the name POR)--if you sandblast it nice and pretty,it still works OK,but the rusty stuff I just slopped it on after only scratching it with a wire brush seemed to harden to a strong "crust".I've seen others pour it on fiberglass cloth and patch holes in floors with it,I prefer welding or brazing a patch in first,then sealing it with that method.It does harden the cloth pretty strong by itself.I used it on the bottom of the doors on my 74 plow truck--should have done the INSIDE too,it rotted from the inside out /forums/images/graemlins/angryfire.gif!.The gloss black will fade rather quickly to a flat black when exposed to the sun,but sun doesnt seen to affect the rust prevention qualitiy of it.
I know that long after the rest of the truck is corn flakes on the ground,the floors and whatever else the POR is on will still look new! /forums/images/graemlins/whistling.gif