POR 15 and other thoughts

[Frankenpez]

Gents

Starting to do a little work on my 70 Cutlass. Had it up on the rack today and really looked over the frame and underbody areas. The frame is real solid, but has a scale of typical surface rust all over it. Also, some seamed areas of the under body have some surface rust. I have no experience with POR15, is this the best product to use if I wire brush these areas and paint them over? I am not, and won't for a long time, doing a "frame off" even though that would be the best way to handle this. Just need to get somewhat of a handle on stopping the rust from getting much worse. Seems to me the last time I had my hand in an old car (late 80s/early 90s) there was a product that you sprayed on rust and it turned it black, meaning it was being neutralized? Is there such a thing?

Looking for recommendations-undercoating, paint, or POR15.

Also, how tough is POR15 to use? I haven't looked into it at all yet.

Thanks for any tips.

[ijasond]

I don't have a lot of experience with POR15, but I don't believe it will convert the rust. Use a wire wheel, then a rust converter(the stuff you referred to that turns it black) & then paint it. The rust converter is basically a phosphoric acid solution that eats away at the oxidation. I've used all kinds & one of the most effective I've seen is actually available over the counter, I got some at auto zone. I believe its made by Kleen Strip.

[Lady72nRob71]

I have heard that POR15 IS the best to use. They have a good website at POR15.com. Some of their paint can be applied right over rust (after the loose stuff is removed).

They also have "chassiscote black" that can be applied that mimics the factory semigloss (but is too shiny IMHO.)
If you look through some of the pictures in my link below, you can see some before and after results. I used the standard clear and the chassiscote. This was my first experience with POR15. I did not use all their prep chemicals, as I cleaned it all with other stuff. The directions even said some of it can be put on right over rust. Bare metal may be another story. Download their instruction sheets and go by them.

Use cheap disposable brushes, as cleaning them is impossible. Wear thick nitrile gloves and old clothes. If you get it on your skin, you will have to wait 2 weeks for it to wear off. It is like painting with epoxy. The fumes are not too objectionable and do not accumulate too bad in an enclosed garage (though I would not recommend that.)
If you get POR15, try getting the small cans - they are convenient.

[Oldsguy]

I agree with Rob, the way POR15 works is that it seals out all possibility of external water intrusion, it will not convert the rust however as was stated. A possibility is to use converter, then topcoat with your favorite enamel to make a hardened exterior shell. I have used both products but not together.

[joe_padavano]

Also keep in mind that POR is not UV stable and will turn chalky over time if not topcoated.

[Frankenpez]

Thanks for the advice. I think I will use a rust converter everywhere I can get to, after wire brushing/wheeling. Then just hit it with some decent paint.

Is there any reason not to use an undercoating along the frame areas, and the underbody? Or, would paint be a better way to go? I don't know if the typical undercoating in the spray cans is all that good of a product.

Thanks again.