need some help with floor plan fix, peeling the coating, POR15, etc Options

[914 RZ-1]

The M/C leaked all over the floor plan. There's some rust as well. Before I put back everything I thought I would clean it all up.

1. What is the best way to get all the coating off the floor pan? It looks like some sort of asphalt/tar paper. It seems to be peeling off okay with a putty knife. I'm guessing I use some sort of solvent to get the remaining gunk off? Heat gun?

2. I have a kit that has cleaner/degreaser, metal prep and POR15. I also want to reseal around whatever that is (plug?) in the middle with some seam sealer. What order is this all applied?
-cleaner
-prep
-POR15
-seam sealer

OR
-cleaner
-prep
-seam sealer
-POR15

Or some other order?

3. I was going to leave the POR15 as the final coat, but do I need to paint over it? The car is silver/gray, the POR15 is gloss black. It's under the carpet and under the floor mat, so it will not show. I'm more concerned with keeping the rust at bay.

4. Where should I stop the painting? At a seal? At one of the changes in contour of the floor pan? Please note that the car was in an accident many years ago (before my ownership) and was repaired, but the floor pan is still a little uneven. My concern is that the paint will wick under the tar paper, but is that even an issue?

Here's a photo, since I know we all like pictures. There is a pile of tar paper on the left:


Thanks!
-Jeff
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[technicalninja]

POR15 has an expensive metal prep called Metal-Ready.

It is phosphoric acid based.
Their website makes it sound totally safe.
"This metal-etching rust neutralizer is not caustic, corrosive, toxic or flammable."
What they didn't say was not acidic...

The first use of phosphoric acid for me was a early Alfa spider that my father did a multi-color paint job on. I was 12 years old and helping him prep the bare metal car.
We used Dura-Etch which was phosphoric acid based.
It was dirt cheap at the paint shop so POR15s Metal-Ready is an expensive re-use of a old product.

What I learned from that Alfa is to never ever lean on a windshield as I broke the one in that car...

[Superhawk996]

POR15 has an expensive metal prep called Metal-Ready.

I’ve used Metal Ready too. It has zinc in it in addition to the phosphoric acid. Ospho is phosphoric acid without the zinc.

Used properly, Metal Ready holds off atmospheric humidity and yellow flash rust pretty well. Ospho will hold off rust but only by leaving it to dry in the panel. Then you need to go back and re-wet with Ospho, remove excess, neutralize, dry and paint before flash rust occurs.

Different tools for different jobs but there are times I prefer the Metal Ready.