Por 15 to protect car

[Aprules2]

I have a week before my car goes into the body shop to get painted. After pulling off the Vinyl top I noticed some surface rust in a few spots, thankfully no rot. Now the top was done once before and who ever did it D/A sanded the whole roof then skim coated it with filler to make it nice and smooth before putting the previous top on. I asked the top guy and he said it was always standard practice at his shop too. My question is has anyone just sanded out all the rust real well did their filler to make it smooth and then painted everything with POR 15 to seal it up. I already lost one Caddy to a rotted roof, Id like a little insurance. I was considering also doing inside the doors and the bottom pinch welds, the backs of the skirts, inside the wheel wells and behind all the wide trim at the bottom of the car. I figure the wide trim will always be covering it so it wont matter if its not the exact same paint the rest of the car is painted with. I love my car and Id like it to last me as close to forever as possible. Ive used POR 15 on floor boards frames and engine compartments and its honestly bullet proof it never rusts or peels. But Ive never used it on body panels or over filler does anyone have experience with it?

[chevyunger]

I think it works only on metal. So use it before the filler.

[Aprules2]

The manufacturer actually recommends doing the filler over the POR 15 but after doing a little Google search most people have issues with adhesion. So I am a little leery about it. But Ive had it stick to things that I didn't intend to coat, I can tell you it sticks to anything and wont come off with out a fight. I broke 2 razor blades trying to scrape it off a back window, I ended up using air craft stripper to get it off, and glass is very non porous.

[Roadmaster75]

POR-15 chemically transforms rust into an inert material …. to that end, it is not a paint.
It will provide no additional protection if you paint it over filler.

I've used it on some really nasty pieces in the past and it works really well.
I've got a Willys-Overland Jeepster that got POR-15 all over it's floor boards
& entire gas tank in 1999.  Still looks like the day I did it.

It will fade in UV light, but, that is only cosmetic & it will not rust again.  Heed the warning on the top of the can…

"if you get it on your skin …only time will remove it"

mike

[Aprules2]

I can vouch for that. The first time I used it I thought it would be like every other paint, I could put some thinners or carb cleaner on my hands and wipe it off. Needless to say I didnt wear gloves I had it on my hands for my cousins wedding 2 days later lol. Also if you get it on the rim of the can and close it. It pretty much welds the can shut.

Its non porous when it dries if it was over the filler wouldn't it deprive it of oxygen and keep it from rusting?

On the site it says "POR-15 works because it chemically bonds to rusted metal and forms a rock- hard, non-porous coating that won't crack, chip, or peel. It keeps moisture away from metal with a coating that is strengthened by continued exposure to moisture."

When I spoke to them over the phone they said they never tested it on top of anything but steel, they said they thought it would stick they just didnt know if it would last or not. In the past when I did use their products they didn't have the best tech support, usually they quoted the web site, and we had trouble but we figured it all out from trial and error. The only reason Im nervous is I dont get a redo on this its going for paint Friday and that's it.

They sell a primer they claim will allow car paint to stick to it, but I have no experience with it and Id hate to have paint flaking off the car. So Im hoping someone here has been through this and can help.

[txturbo]

If it's just surface rust covering the whole roof use the por-15 on it. If some of it is still painted then you need to strip it all down to metal, use metal conditioner then several coats of epoxy primer. If there are rust pits then you can use filler over the primer or Por-15. Either way, don't put body filler on bare metal or rust.

[Aprules2]

Its a few small spots of surface rust and a few lines from the first guy who installed the top. He took his utility knife and dug straight in to the paint to cut the original top off. Thank god it was in the garage right after and didn't move otherwise it would probably be pure rust.

I don't know much about its history the previous owner told me the car was all original except the top, which he had replaced and had the rust repaired before parking the car. Now that Ive had the car apart, I can see the nose was metallic blue under the trim, the drivers quarter had a dent pulled at one time and there's a dent pulled on the passenger side by the tail light. This explains why the car had such pristine paint and a new top on it. The doors and fenders were out of adjustment and I had to readjust them too. My guess is the car got hit he got it fixed cheap, and was unhappy, by this point it was 4 years old and he felt like he was driving junk so he parked the car.  He bought a new 80 Sedan DeVille to replace the car. The funny part is the paint looks smooth as glass and the body looks straight as an arrow, when I took it to body shops for estimates they didn't think there was any filler in it, they just said the panels are aligned poorly. I had it checked by a body man and the frame is straight, so there's no reason for bad panel alignment.

Now that the whole interior is out of the car I did some inspecting of the roof, it is all steel and not rotted thankfully. From what I see half the roof was repainted during the quarter panel repair and is nice and smooth the other half was untouched they just sanded the paint off put filler on smoothed it and sprayed it with rustoleum. I am a crap body man, so my plan was just to sand the rustoleum off, sand all the rust down, cross hatch the filler to make it smooth and coat the whole thing with POR 15. If that's not an option Ill just pay the body shop extra to do it up.

[txturbo]

If it's rustoleum it needs to come off to bare metal. I've heard of compatibility issues with that and regular automotive paint.