Floor pan prep options.

[rcl700]

Hello all, I looking for some advice on preping and sealing the floor pans in my p15. I removed the seats and pulled back the carpet today. I found some rust but feel that for its age it's not too bad. 

I'm thinking I can wire wheel it and hopefully seal and paint it. I interested in what products other members have had success with. 

 

Some options I was thinking of;

•Ospho- rust converter then paint

•Rustolium rusty metal primer

•Por-15 - need to hose out the car with metal prep and cleaner.

•eastwood rust encapsulator 

 

What has worked for you, or not worked?

Also have a few small rust pit holes to fill. 

 

[Bob Riding]

for the underneath - truck bedliner in spray cans.

 

[uncleaud]

Master Series silver, or Rust Bullet! Both are an industrial type bridge paint. They require minimum prep work, are uv resistant. Either one are remarkable products. All you need to do for prep is remove as much loose rust as you can with a wire brush and brush it on. It will actually strengthen pinhole areas if they aren't rotted out. Do yourself a favor and google them. They are the only rust repair product that I have used in my lifetime that actually does what they claim.

 

They are ideal for the type of rust in your photos. 

Edited October 28, 2023 by uncleaud

[plymouthcranbrook]

I used POR-15 about 20 years ago on my 52 Plymouth.  It sure is a PITA but there hasn’t been any return of rust I have ever found.

[D35 Torpedo]

Wire wheel it, that's a given. Then, brush on a few coats of rustmort. Finally, brush on rustolium, or whatever paint floats your boat. But brush it on to ensure a good, thick coating that will last.

[Sniper]

I would suggest before you put the carpet back on and after you're done prepping your floor pans you consider some sort of sound editing material as well. I prefer the roll-on elastomeric coating they use on roofs.

[Los_Control]

I have had good results with ospho.

I remove as much rust as I can, Using a wire cup wheel on a grinder. I also have 36 grit sandpaper for my orbital sander. Sometimes it is a hand held wire brush or sandpaper.

 

Then I have disposable plastic butter bowls ... I always keep a few in the garage. I like to pour a little ospho in the bowl and then use a brush to apply it.

I get the cheap $1 nylon paint brushes from the dollar stores. You can get a nice even coat this way.

They have ospho in a spray bottle, I find it wasteful and streaky .... brush is better.

 

I had to weld in some patches also, when done welding I then used seam sealer around the welds to take care of any missed pin holes in the welds. Most of my original seam sealer around the floor edges was missing or in poor condition .... I dug it out and replaced it. This also would work on the rusty pin holes.

I had a few where the metal was strong, the holes were too small to bother welding.

 

For paint, I used Rustoleum paint, applied with the same nylon brush I applied the ospho with. Ospho will not hurt the brush, the paint will melt the brush after a hour or so of use .... just throw it away when finished with it.

The Rustoleum paint is DTM (direct to metal) Primer is not necessary here. IMHO. .... I would rather just apply 2 heavy coats of paint with the brush ... It also claims to be rust preventative ..... you already took care of the rust with ospho.

 

I treated my whole truck with ospho during paint. The frame, suspension, axles, floor all using DTM.

The body panels were also treated with ospho while bare and waiting for paint, then they got a few coats of rusty metal primer before paint.

[Bob Ritter]

Safety first, you want to use a face mask and rubber gloves. Find a good ventilated area to work in. Next use a vacuum to clean up the loose rust as you go. I also like the wire cup brush to loosen the rust. And the Por-15 is a good product to work with, but there is a lot of choice out there to choose from. When I completed the flood I used the paint that they use on the truck bed liners, this is real touch stuff and can be spray on bear metal. After the paint dried I covered the floor with sound deader which is water proof. The cause of most of the rust damage is the cowl vent leaking, it would be wise to change the gasket and to make sure the drain pipe is not plugged up. It is going to be a lot of hard work, but make it something you can be proud of.

By the way you are very fortunate not to have install in patch panels...

[kencombs]

Lots of good advice here.  Removing as much rust as possible by mechanical means is best IMO.  I use a cup brush also, 6" on my big grinder, 3" on smaller grinders, regular wire wheels (not cup), maybe a little media blast in crevices, whatever gets you to mostly clean with some you just can't convince to come off.    The rust and paint removald disks on a little grinder work well.   these are also available in smaller sizes for die grinders and drills.   Then apply Ospho or similar.

 

I vary from others advice at that point as I'm a big fan of Epoxy primer applied with a brush on horizontal surfaces.   Since it cures, not drys, heavy deposits still become firm all the way to the bottom fairly quickly.   Some drying paints will take forever to do that.   Epoxy is much more flexible than some of the miracle products and doesn't chip. 

 

After that cover all seams with a sealer.   The sealer is after the epoxy 'cause the epoxy fills small crevices better.   I don't use the expensive sealer, just the solvent based tubes from Auto Zone, that's about all I buy there.  Then apply a sound deadener and insulation of your liking.    Lots of choices there too.   Some swear by peel and stick flashing from the home stores, some swear at it.  Most of the stuff made for cars is either butyl or tar based, like flashing.    Other choices are the available.   I just pick what fits the vehicle and my budget.  My truck will get at least 3-4 different kinds, roof cab walls, floor, firewall under seat will have different finished.   May try Snipers suggestion above.

 

 

 

 

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[rcl700]

49 minutes ago, kencombs said:

Lots of good advice here.  Removing as much rust as possible by mechanical means is best IMO.  I use a cup brush also, 6" on my big grinder, 3" on smaller grinders, regular wire wheels (not cup), maybe a little media blast in crevices, whatever gets you to mostly clean with some you just can't convince to come off.    The rust and paint removald disks on a little grinder work well.   these are also available in smaller sizes for die grinders and drills.   Then apply Ospho or similar.

 

I vary from others advice at that point as I'm a big fan of Epoxy primer applied with a brush on horizontal surfaces.   Since it cures, not drys, heavy deposits still become firm all the way to the bottom fairly quickly.   Some drying paints will take forever to do that.   Epoxy is much more flexible than some of the miracle products and doesn't chip. 

 

After that cover all seams with a sealer.   The sealer is after the epoxy 'cause the epoxy fills small crevices better.   I don't use the expensive sealer, just the solvent based tubes from Auto Zone, that's about all I buy there.  Then apply a sound deadener and insulation of your liking.    Lots of choices there too.   Some swear by peel and stick flashing from the home stores, some swear at it.  Most of the stuff made for cars is either butyl or tar based, like flashing.    Other choices are the available.   I just pick what fits the vehicle and my budget.  My truck will get at least 3-4 different kinds, roof cab walls, floor, firewall under seat will have different finished.   May try Snipers suggestion above.

 

 

 

 

 

Thanks for the advise. After chipping away some of the old seam sealer with a hammer and standard driver, I think I'm going to need to remove most of it. There is more rust under the old sealer. So I'll keep chiping away?. I have 1/2 gallon of Ospho so I'll plan to use it once I get the rust ground down. 

 

I guess I'll probably need to just gut the car all the way through the trunk. 

[Dave72dt]

Seams have two sides to them.  the bottom side needs to be done as well.

[Los_Control]

7 minutes ago, Dave72dt said:

Seams have two sides to them.  the bottom side needs to be done as well.

Glad you said it, I did not have the heart to tell them everything done on top .... needs to be done on the bottom also.

 

It really is not a pleasant job. ....Last area on my truck that needs to be painted. .... been waiting til I got the new floor welded in and finished on top.

 

Just get it high enough on blocks so you can lay on your creeper and scoot around .... wear eye protection ... always ..... Dirty job but only needs done once.

 

Some cars have undercoating on them .... what a mess that can be if it needs removed.

[rcl700]

37 minutes ago, Los_Control said:

Glad you said it, I did not have the heart to tell them everything done on top .... needs to be done on the bottom also.

 

It really is not a pleasant job. ....Last area on my truck that needs to be painted. .... been waiting til I got the new floor welded in and finished on top.

 

Just get it high enough on blocks so you can lay on your creeper and scoot around .... wear eye protection ... always ..... Dirty job but only needs done once.

 

Some cars have undercoating on them .... what a mess that can be if it needs removed.

One step at a time..

[Bingster]

When I did my '47 DeSoto I unscrewed every piece of sheet metal that could be removed, sand blasted, primed and finished up with Rustoleum Black, I think. I was new to the game and might have used Eastwood. I still have a few cans of theirs I never used. But I would definitely go with Rustoleum. I like to use gloss black for easier cleaning properties.  I'm certain you can get better than Rustoleum, but I feel it's the bottom-line good choice.

 

I will tell you that I've used their Rusty Metal Primer and I have had rims and stuff sitting outside for years and they're still the same as the day I shot them.  I've found it to be awfully durable stuff. I'd never use it on the exterior finish coat of the car as a primer, but for something like the floorboards that get covered up anyway with carpet, I think that when brushed on and worked in well with a heavier coat it'd be a fine choice.  You might even double coat it, waiting a few days in-between.

 

[Ivan_B]

I went with a completely different approach. The problem with most coatings is that you need to have a factory-clean metal, otherwise, it will not work well. Moreover, it is difficult to clean rusty metal seams, etc. As for the bead-liner spray, and other thick coatings - these are even worse (in some way) because they look perfect on the outside while you have rust going on underneath.

 

Once I had the interior out, I used liquid/oil undercoating. There are a few options available, I went with the Canadian Rust Cure Formula 3000 because it has great reviews. Ordered a gallon jug and a couple of spray cans. Applied it mostly everywhere with a brush and sprayed inside the doors, etc., where I could not reach. I really like the way it works. You don't have to clean anything, it just soaks what ever you have and, supposedly, stops it from getting worse. A small drop, at high ambient temperature, is really spreading well into all kind of places. The only disadvantage is no protection from elements. So if the car is driven in adverse weather, this is supposed to be applied again once per season. In my case, however, this is not applicable.

 

I placed some construction cardboard over it, so that it does not soak up into the upholstery. I am planning to do the outside of the car, rockers, and other hidden cavities, a bit later.

[Eneto-55]

I doubt if most of these products were available back in 80 -81, but if they were, I hadn't heard of them, or considered them to be too expensive for what I then considered to be just rebuilding an old car as a daily driver.  But I did have the body off of the frame, and used a wire wheel (& a hand wire brush) to clean off as much of the rust and scale as possible. (I thought the car had very few pin holes in the floor until I started in on that process...)  Then my dad borrowed an undercoating "spray gun" from the dealership where he worked in the service parts department.  The undercoating came in 1 quart cars.  I did the whole bottom, and inside as well.  Then I painted the inside with enamel, with paint we mixed as close to the body color as possible, with what we got from left over pain from the dealership paint shop.  

 

Then the car sat in the same spot until 5 years ago, when we moved it from Oklahoma to Ohio.  The bottom still looks as black and beautiful as ever.  This was a tar-based undercoating material, used before they came out with rock-guard and the such like.  None of it is clacked loose, so I doubt if there is any rust forming under it.  But the car has never been driven at all since, nor been in the rain. 

 

Should I coat the underside with enamel paint yet, or just leave it as is?

 

(I might have mentioned this before, but this method my grandpa used to fix rust holes in his grain storage tank might be helpful for closing pin holes.  He painted the area to be patched with enamel paint, just whatever he had.  Then while it was still very wet he laid on a piece of heavy fabric, and soaked that with paint as well.  The fabric essentially just becomes a reinforcement embedded in the paint, sort of like fiberglass matte in the resin.  In his application, these areas were exposed to the heat of the direct Oklahoma sunlight.  Lasted for years, even in that environment.)

[Ivan_B]

1 hour ago, Eneto-55 said:

None of it is clacked loose, so I doubt if there is any rust forming under it.  But the car has never been driven at all since, nor been in the rain. 

It depends. Corrosion can form just from the humid air, and you will not see anything under the undercoating, until the metal is completely gone and you poke it with a screw driver. Even old guns stored inside bags with cosmoline sometimes rust because there are air pockets in there...

 

1 hour ago, Eneto-55 said:

The fabric essentially just becomes a reinforcement embedded in the paint, sort of like fiberglass matte in the resin.

I do not believe that this is a proper way to do body work. Same as fiberglass, by the way. This is just an old-school DIY hobby molding material, back when 3D printers were not available

Edited October 29, 2023 by Ivan_B

[Eneto-55]

2 hours ago, Ivan_B said:

It depends. Corrosion can form just from the humid air, and you will not see anything under the undercoating, until the metal is completely gone and you poke it with a screw driver. Even old guns stored inside bags with cosmoline sometimes rust because there are air pockets in there...

 

I do not believe that this is a proper way to do body work. Same as fiberglass, by the way. This is just an old-school DIY hobby molding material, back when 3D printers were not available

As to the first paragraph, it is currently still as solid as it was when I did it.  It's been over 40 years, longer than the car was old when it was applied.  If it was rusting under there all this time, I think I would have noticed something by now.  When we hauled the car out here to Ohio, I packed a lot of heavy parts inside the car, extra head, intake & exhaust manifold, flywheel, etc.  A whole shipping trunk full of extra parts from my other P15.  I have been both in and under the car recently, and a lot when we were loading it, because I did the under-the-car part of the job of wrapping the entire car, front to back and side to side (wide pallet wrapping plastic).   Admittedly the climate is worse here in Ohio than it was in Oklahoma.  (Did the wrap job because the windows are out of it.  Come to think of it, I believe it DID rain on the trip home.  I wasn't along for that part, as my son-in-law had to get back to work, and he drove the trailer rig back while I stayed longer, and brought a full load of other parts in my 2010 Dodge Grand Caravan - had all of the seats down in the floor except for the third row, which I had taken completely out, to lighten the car and make more room.  Then I made another trip out there by myself 4 months later, for another minivan load of stuff.)

 

Regarding the 2nd paragraph, I didn't do this (the saturated cloth deal) on my own car, nor would I.  I replaced metal with metal, in all of the places where there were any pin holes at all.  I only mentioned it in case someone else doesn't want to weld up all of the pin holes, and is not doing a frame-off rebuild job as I did.  As far as sealing out water and fumes, I would maintain that it would be as durable as the paint used.  Remember, I was only talking about pin holes, not cracks or places where it is so deteriorated that there would be flexing.  If I were doing the job now, I wouldn't use undercoating, because I think that what is available now is probably a better option.  I'm a pretty picky person, and I did that with the body off of the frame, so I got it covered everywhere.  But it's also a solid car, having spent its entire life in Oklahoma.  (At least I know that it was originally sold new there, and that's where it was when I bought it, March of 1980.  Cars don't rot out there like they do other places, certainly not like here in Ohio.)  I just don't plan on stripping the car down again, scrapping the undercoating off, and doing all of that over again.  At this point, those repairs will out last me, and then some. 

[FarmerJon]

On 10/28/2023 at 11:12 PM, Ivan_B said:

I went with a completely different approach. The problem with most coatings is that you need to have a factory-clean metal, otherwise, it will not work well. Moreover, it is difficult to clean rusty metal seams, etc. As for the bead-liner spray, and other thick coatings - these are even worse (in some way) because they look perfect on the outside while you have rust going on underneath.

 

Once I had the interior out, I used liquid/oil undercoating. There are a few options available, I went with the Canadian Rust Cure Formula 3000 because it has great reviews. Ordered a gallon jug and a couple of spray cans. Applied it mostly everywhere with a brush and sprayed inside the doors, etc., where I could not reach. I really like the way it works. You don't have to clean anything, it just soaks what ever you have and, supposedly, stops it from getting worse. A small drop, at high ambient temperature, is really spreading well into all kind of places. The only disadvantage is no protection from elements. So if the car is driven in adverse weather, this is supposed to be applied again once per season. In my case, however, this is not applicable.

 

I placed some construction cardboard over it, so that it does not soak up into the upholstery. I am planning to do the outside of the car, rockers, and other hidden cavities, a bit later.

There are some cool anti-rust oils on the market, and i would think they would do a good job seeping into seams, but a major disadvantage to me would be that butyl rubber sound deadener would likely not stick to panels treated with oil. 

 

I went with physical removal of the minor rust (grinder with cupbrush, 80grit sand paper) then rust encapsulating paint, with 80mil butyl rubber sound deading, before laying down foam pad and carpet. 

The Siless brand is made in Europe and can almost always be found cheaper per square foot than the roofing 'peel and seal' products, is thicker, and has less risk of stinking.

If you go this route, make sure you keep all your access panels removable by insulating them separately. 

 

[Ivan_B]

3 hours ago, FarmerJon said:

...butyl rubber sound deadener would likely not stick to panels treated with oil. 

For sure... If you need some sound insulation, you'll have to rely on laying down some loose sheet material. Disadvantage? Maybe, but it can always be easily removed for inspection/service later on