Hey Matt.

I've used a combination of POR-15 and new sheet metal to rebuild large holes in my car's floor and the rear wheel-wells. Right now I'm playing catchup on more superficial spots.

What I do is remove as much weak and loose metal as possible. Then I clean the heck out of all surfaces that will receive the paint using a cleaner that POR-15 sells and recommends. Then I either use their clear sealant paint to cover the rusted areas or I brush on their POR-Patch, which is a thicker version of the paint, on smaller areas.

If it's a hole that I'm rebuilding, I'll either place some epoxy putty over the hole (while the POR-15 is not fully cured but tacky so the putty holds in place), or screw or rivet fresh steel in place.

And about that fresh steel...it needs to be treated with something called Metal Ready which etches fresh, smooth steel and places a coating of zinc phosphate on it. Much like primer, it gives the POR paint something to grab onto.

Once that cures after a week or so, I seal any seams or edges with POR Patch. Then I prime and paint if it's on the outside of the car, or top-coat it with their undercoating.

Overall, I've been pleased with the stuff. It works well if you follow the directions. And without it, my car would have been scrapped years ago.

I hope this helps; let me know if you have any questions!
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Mike F - 1984 244 DL - 296,000 miles
Original engine, transmission, drive train, starter
Undergoing reconstructive surgery with POR-15