Posted by Doc Dave on Sunday, September 04, 2005 at 1:40PM :
In Reply to: That shoots my theory... posted by chriscase on Sunday, September 04, 2005 at 9:59AM :
When I bought the truck the guy before me had started to restore it and lost interest. He had painted the rear half of the frame in POR.
I painted the fuel tank and a few other parts in POR, but then I noticed what looked like rust-through on the rear crossmember.
I decided to switch to urethane then.
When I tried to sandblast the POR, it is very hard, but once you get under it it at an angle, it delaminates off the metal in strips, sometimes long ones. It does not appear to bond anywhere near as well as epoxy primer to the metal.
I was also really surprised at how fast the lye took the POR off, and how resistant the urethane was to it.
I have concluded that POR is very hard and thus resistant to rock chips, and it is very easy to use compared to sandblasting, etc.
However, I am concerned that if you get rust started under it, it would creep/spread under the POR because of the questionable bonding.
I think the extra work pays off in rust resistance and durability with painting with epoxy primer and urethane or polyurethane (Imron).
JUst my opinion, I am not a paint expert.
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