Waterproofing the floorpan

[FredC]

I've got a 69 Targa and short of replacing the entire floorplan which is NOT in the immediate future, I'm trying to seal the floor against a number of small pinholes and cracks that let in water in the rain. In searching for a product which could be sprayed or painted on, I've come across an epoxy sealer used to line pick-up truck beds...call me crazy but could this be a solution? It's water-proof, can be sprayed on to 1/4 inch thickness, hardens like steel, then glue on underpadding and the new carpet...voila! I'd appreciate your feedback on this one. Thank you. (I've had the car for 25 years, seldom drive it in tha rain, always store it indoors and plan to give the car to my children, so don't worry about re-sale value...

[scottb]

I sounds as though that might be a short term fix, but it also sounds like you have some pending rust issues that should be addressed first. Have you considered the Por-15 products that neutralize rust? That might be the first thing you should do, and then you might be able to coat everything with something like you described.

[Paulporsche]

I agree w/ Scott in that you should first make sure the existing rust doesn't spread. Traditionally you would weld in new metal, but under the circumstances, why not try a new higher tech material like you describe.

I am even wondering if the liner material would be good sprayed on the underside, encapsulating the rust top and bottom.

Can you do this yourself? Or do you take it to an applicator's shop?

If you do it, show us some pics and give us an update.

[JBO]

That should work. You can also use a spray on rubberized undercoating product, but it will not harden like the truck bed stuff. I think the suggestion of doing the top and bottom is a good one.

[FredC]

Thanks for the feedback. I like the top/bottom idea. I do not think I can lose, in case that it does not work, out comes the torch, we'll replace the floorpan! In any case, I am simply trying to keep out the moisture, this application sounds "solid"...i'll keep you all posted.

Fred C.

[notfarnow]

A few years ago I had an 88 Honda civic that someone had done this to. If anything, it seemed to have worsened the rust, by trapping moisture between the coating and the steel. Areas that hadn't been sprayed with the stuff were rusty, but not completely gone. On areas that had been coated, the stuff was peeling off with soggy chunks of rusty steel. Not pretty. My concern would be that you may be trapping mointure IN, and accelerating the rust. However, if you apply the stuff when the car is DRY, and it's kept DRY, maybe it wouldn't be so bad. I'd be tempted to take the Por-15 route though.

[Tex3]

how about Wurth coating??? I have used it in my trunk and gas tank looks fantastic and is O.E.M for porsche.

just my 2 pennies

[competentone]

Originally posted by notfarnow
A few years ago I had an 88 Honda civic that someone had done this to. If anything, it seemed to have worsened the rust, by trapping moisture between the coating and the steel. Areas that hadn't been sprayed with the stuff were rusty, but not completely gone. On areas that had been coated, the stuff was peeling off with soggy chunks of rusty steel. Not pretty. My concern would be that you may be trapping mointure IN, and accelerating the rust. However, if you apply the stuff when the car is DRY, and it's kept DRY, maybe it wouldn't be so bad. I'd be tempted to take the Por-15 route though.

Excellent thought. But I'll add that no matter how well you think you've gotten rusty metal "dry," it really isn't; the red oxide of rust has a water molecule chemically attached -- this is what makes it unstable and why paint won't stick to it.

The trick of rusty metal primers and rust “reformers" is that they chemically interact with the rust and drive the water molecule off -- and even those can give problems if they are applied without good surface preparation, such as if they applied over flaking rust.

I'd also ask, are you sure the water is coming "up" from the floor pan? Sometimes a leak around a window or door can seep along a single small line to the floor; the floor gets wet making it look like the water is coming "up" from the rust holes, but it's really the water seeping down which has caused the floor rust in the first place!

[randywebb]

slight change:

The trick of rust “reformers" is that they chemically interact with the rust and drive the oxygen atom off from the FexOy (= rust) that is formed when water interacts with Fe. In other words they reverse the chemical oxidation reaction. These opposite sorts of rxns are called reductions, hence the other term for these things, rust "reducers".

[scottb]

Rust? Por-15. Enough said.

[SLO-BOB]

I've actually done this. My 2002 had a mildly rusted floor, but I wanted to make sure it didn't get any worse. I first removed all the tar and glue-a real pita. Then, after it was sqeeky clean I did the three stage p.o.r. treatment-essential. After that I had it professionally coated with bed-liner. It looked good enough to leave out the carpet and thus not trap moisture. I received many compliments on it's appearence. Feel free to pm me for specifics.

[RickM]

Originally posted by FredC
....in case that it does not work, out comes the torch, we'll replace the floorpan!
Fred C.

Good thought. You may put more effort in trying to salvage and protect what is there.

[competentone]

Originally posted by randywebb
slight change:

The trick of rust “reformers" is that they chemically interact with the rust and drive the oxygen atom off from the FexOy (= rust) that is formed when water interacts with Fe. In other words they reverse the chemical oxidation reaction. These opposite sorts of rxns are called reductions, hence the other term for these things, rust "reducers".

Rust -- as we encounter it in our day-to-day lives -- really is NOT just a simple form of "iron oxide." Rust represents both iron oxides and hydroxides -- the iron oxides alone are fairly stable.

Here is some basic chemistry on the subject in layman's (high school chemistry) terms:
http://encyclopedia.thefreedictionary.com/Chemistry%20rust

It is my understanding that most of the rust converters (better term than the "reformers" I used earlier), are dealing with the hydroxides not the oxides, using phosphoric and/or tannic acids. The oxygen is chemically bonded to the iron quite strongly, it is normally separated from iron above 2000 degrees. A little iron chemistry:
http://encyclopedia.thefreedictionary.com/iron