Adam1031

My '85 has some rust on the underbody and floorpan. I'm going to have it pressure washed and undercoated. At first I was concerned about how this might affect the resale value, but it seems like a future buyer would rather have undercoating than floor pans with rust coming through. I'm also hoping that undercoating will make the cockpit a bit quieter.

I've heard wonderful things about this POR-15 stuff. Anyone have any feelings one way or the other about a POR treatment before they spray on the undercoating?

cv67

Undercoating absorbs moisture.

POR is good stuff finicky on prep and not cheap, have used it for yrs. What about shooting on a truck bed liner or something to that effect, doubt it would lose you 1 penny of resale, if anything may be a nice selling point.

mtwoolford

Most things that are designed to stabilize rust contain phosphoric acid and work by converting rust, ferrous oxide, which is brownish, soft, unstable and self perpetuating, into ferrous phoshate, which is black, hard and stable.

To an extent, all these products are very similiar; however there are differences. On board ship we use Corroseal which I suspect is very similiar to POV-15, in that it is carried in a binder and is painted on and is intended to serve as an actual, permanent coating. A primer, if you will, for the paint coatings yet to come. These coatings work very well, but are unable to penetrate the underlying rust to any significant degree, and as a consequence require mechanical removal of the underlying rust.

Of course, it is desired to remove of as much rust as possible. However you can only remove just so much mechanically; media blasting is very effective, but may not always be possible.

The hardest rust to remove is not the surface rust; the hardest to remove is the rust in the pits which have penetrated into and below the surface of the metal. For this you need something that is liquid, as JASCO Metal Prep. A liquid will soak into the pits and attack and stabilize the last remnants of rust.

You're right to deal with these rust issues. At this point, they appear to be mostly cosmetic (am I right?), but left unattended, they will do nothing but get worse.

Adam1031

I was under the impression that they could treat it with POR and then spray on a coating similar to that of a truck bedliner.

samsonb

I don't see where you would have rust at. The floorpans are made out of SMC, which is a type of fiberglass. The rear of the floorpan is made out of aluminum.

There is a metal shield riveted to the front edge of the floorpan I guess to protect it from rocks. I don't know what that is made out of.

powerpigz-51

There is a product called "Jasco" that is a greenish fluid (phosphoric acid) that you can brush or spray on, turns the rust black. Used to be able to buy this at a hardware store. Then I would use DTM (direct to metal) Epoxy, and then topcoat of choice (bedliner or other). POR 15 is good, but very expensive. The DTM epoxy primer is good stuff, hard as nails when dry. It can be sprayed or brushed on.

jeffp1167

the floors are only smc in front of the seats, under them they are metal.

samsonb

Yes, as I was saying the rear of the floorpans are made out of aluminum. Aluminum doesn't rust.

Though there is a small piece of metal rivited to the front edge of the floorpan on the outside. I don't know what metal that is made out of. There are alot of C4's with undercoating on the floorpans. Must either have been a factory or dealer option.