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Posted by Doc Dave on Sunday, July 20, 2008 at 08:19:13 :
As for the relative merits of POR vs other coatings for our trucks, I wanted to share my experience as well as the results of an "experiment" I conducted.
I won't comment on powder coating as an option, as I feel I do not have enough knowledge about that subject.
When I bought and started the restoration on my truck, I saw that the previous owner had started to refinish the frame in POR. Some of the frame was coated in it, some was still rusty.
When asked, his comments to me at that time implied he had followed the POR company's instructions as to wire brushing the rust, then the POR company's "metal clean", then POR's "metal ready". Then he followed with the black POR coating as they advise.
After I got the truck home, and some consideration, I decided to blast the frame down and paint it with epoxy primer and paint. I felt from reading on this forum that that was the best way considering everything, if one has the time and tools to handle the job.
While starting to blast, I noticed that when I hit the POR area with the sandblast stream, it lifted off in some places in large sheets of dried coating. There was a great difference in where and how well it adhered to the metal.
Surprised, especially considering the POR company advertising about the product, I devised an experiment of sorts. I took two parts and blasted them to rough metal, removing all rust. With one part I then followed the POR instructions (cleaned and prepped it with their products) before coating with POR.
On the other part I used epoxy paint and hardened urethane (PPG).
After letting both parts cure for about a month, I filled a bucket with hot (not boiling) lye solution, and suspended them in this for 5 minutes.
As the picture shows, the part that had POR on it shed the POR coating within a minute or two, back to smooth metal.
The other part, with hardened urethane over epoxy, looked like I had dunked it in plain tap water. I chipped at the paint and it seemed to have not been effected at all.
Now, I realize that on the trail we aren't going to run through lye puddles, but the dramatic difference in adhesion as shown by this test gives me pause for concern.
Based on this, I would be less inclined to use POR on something that might get chipped or scratched through to the steel under it, or otherwise could get moisture "behind" the coating that might act to lift it off and rust.
IMHO, POR would be alright if you don't have the time or money to do the traditional approach of blasting, epoxy primer, hardened urethane.
One other thing I like about paint is the ease you have in repairing chips, etc. While not sure, I wonder if this would be a weakness of powder coating.
p.s. BTW, I have the POR fuel tank product in my tank and so far have been pleased. I have run the engine weekly now for a year and a half and have not had any sediment come through to the bowl.
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