undercoating for light surface rust

[grumppyoldman]

I'm wanting to preserve the underside of my 41 Ford coupe, but don't want it to look like I'm trying to hide something. What have some of you used to protect the floor pans and frame. I will have to do this by hand as I have no lift, and paint with brush so there is no over spray. Thanks Al

[19Fordy]

Bedliner.
Something like this. https://www.gamut.com/p/rust-oleum-t...FUsvaQodK8YHJw

[mountstimothy0]

I'm using Rust-seal by SEM #39304. It's like $60 a 1 quart bottle but goes a very long way. It's waterly thin. It can be left exposed or painted over. I've used one bottle on 2 cars. All you have to to is remove loose particles. And it turns into a black primer. And looks good if left exposed. 3 coats is sufficient.

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[mountstimothy0]

On an added note. It is applied with a sponge brush or hair style paint brush. For under the car I would use a sponge type because it is so thin

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[mountstimothy0]

As with bedliner it would appear as you're hiding something with the sealer it is a primer and won't hide anything

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[Ford Freak]

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I put POR - 15 Satin Black on mine . Looks great !

[flatford8]

I like something thin,(like the one that has been suggested), so if it starts to rust you can take care of it. The bedliner type products or like the stuff that was Ford used on my '50, rust can be developing under it and you can't see it....... Mark

[Ken/Alabama]

Leave it as it is. It'll last another 76 yrs.

[Kube]

Originally Posted by Ken/Alabama

Leave it as it is. It'll last another 76 yrs.

I read through this thread and quite early started to wonder why not just leave it alone. Ken beat me to the punch (again).
I might add... if you want to preserve this car for future generations, one train of thought might be to stay away from coatings like POR 15, etc. If anyone in the future went to restore this car, rest assured upon removing the coating, they will be swearing up a storm at the guy that got that crap all over the place.

Ken is 100% correct... your car will (no offense) outlast you and me for that matter without doing anything.

[Capt Kirk]

The OP is in Texas and I don't think there's a humidity or salt problem there? I was on the fence reading through this post. On one side, if an old car is eventually going to rust to the ground then I think something should be done to prevent it. On the other side, if we're talking some surface rust that's not going to amount to much over the years then let it be. I wouldn't cake undercoating or bed-liner on it because it won't stop the rust. A thin conversion coat seems to work good. Someone who wants to restore the car in the future is going to appreciate as much original metal as they can get and they're not going to be happy with bed-liner stained with the last vestiges of metal. Do nothing or a thin coat of rust conversion.

[deuce_roadster]

What Kube said x2. A big plus is you don't have to get underneath it and paint with a brush if you just leave it alone.

[Jakno]

We use a product called FLUID FILM. It comes in gallon cans that you can brush or spray on or in 16 oz aerosol spray cans. It requires an application every 12 months or so depending on your climate. Would recommend finding a lift to use if you can.

[cas3]

living in the salt encrusted swamp all my life, i will take the liberty to declare myself a rust expert. i hope you can agree. first, getting wet is not the problem, staying wet IS the problem. meaning, metal when dry will out live us all, and metal that is holding moisture will rust. take a piece of new tin and throw it up on a rock pile. lots of sun and wind and no moisture underneath, it will be fine for decades. take the same piece and throw it on the ground, cover it with leaves and in five years it will be gone. most of the low budget junk i have drug home all my life died from the old rotten carpet and interior material, and leaves when windows are missing. these things hold moisture even in the desert. then, you have four flat tires so the poor thing is sitting down near the earth, or on it, and tall grass all around so no wind, and high humidity on the bottom, rotten leaves on the top...a few years and its bad. so it sounds like you have a good car that never saw any of that, but you still have places that are holding moisture. i agree with the others about "leave it alone", as far as coating the whole underside with some gook, but lets talk some more about moisture. its the enemy, and it is held by dirt which is in the bottoms of the doors, and the seams around where the floor meets the the body. mostly any place that the metal is doubled up for a seam, or two pieces welded together, tend to get dirt in them, which holds moisture, which is the problem. i commend you for your concern, but the best thing to do to preserve old metal is get it clean. take a pic or thin screw driver and a vacuum cleaner and go around all the seams on the floors and clean out the crud, again, its holding moisture. the bottoms of the doors are usually full of crud. ford used some kind of sound deadener that was like tar brushed on the insides of the doors and body panels that is now flaking off and sitting in a pile at the bottom holding moisture, get it out of there!! i live on a gravel road and the township figures 1" per year of gravel is lost due to dust. where does it go? atleast some of it is in the bottom of my doors! i know most guys with a nice original car will cringe at the thought of opening up interior panels to clean them out, but i promise you they are full of crud. doors and bodys have drain holes, make sure they are open. even washing a good car will get water down in the bottom, but you drive it soon and all the heat from the motor and the air movement will dry it out again, IF its clean in the bottom and the seams. also, the death of many old fords is dirt held in the frame where the sections are doubled up. scrape them clean and blow out with air. one step further i do here in the swamp on my modern cars is drill a 1/4" hole in the door jams and rocker panels so i can spray a mixture of diesel and 90wt inside, and then put rubber plugs in the holes. been doing it all my life, and it really slows down the rust. you live in texas, just clean and vacuum out the crud and it will be fine for many decades long rant from the rust expert

[cas3]

i have to add, any kind of undercoating only works if it is 100% dry. if not, you sealed the moisture in, and rust worse than if you leave it alone

[G.M.]

I clean it the best I can and use Rustolium Satin or semi gloss black.
I take the little round spray hole out. The small red straw from WD 40
fits tight in the spray hole. This gives a good wet stream that is small
[n diameter and shoots out at least a foot allowing a good soaking in
hard to reach place and under the floor above the frame. G.M.

[19Fordy]

cas3: Good points but, ................my eyes hurt.

[old46ford]

I wired brushed mine, then used Eastwood's rust encapsulator.

[36coupe]

Originally Posted by Jakno

We use a product called FLUID FILM. It comes in gallon cans that you can brush or spray on or in 16 oz aerosol spray cans. It requires an application every 12 months or so depending on your climate. Would recommend finding a lift to use if you can.

Coming from the northeast as well I would second fluid film or rust check. It stays soft, creeps in the seams and will not trap water. Anything that dries to touch will trap moisture in against the light rust and make heavy rust.

I have seen guys thin tremclad with motor oil so it never dries.
Heat chainsaw oil and spray it.

We have franchise shops that spray rust check, it pretty much disappears after a year but it works.
If you do nothing 10 year old trucks have there frames break in two. We call the eastcoast the rust bowl of North America.

[GB SISSON]

Originally Posted by 36coupe

Coming from the northeast as well I would second fluid film or rust check. It stays soft, creeps in the seams and will not trap water. Anything that dries to touch will trap moisture in against the light rust and make heavy rust.

I have seen guys thin tremclad with motor oil so it never dries.
Heat chainsaw oil and spray it.

We have franchise shops that spray rust check, it pretty much disappears after a year but it works.
If you do nothing 10 year old trucks have there frames break in two. We call the eastcoast the rust bowl of North America.

I'm with 36 coupe and Cas. Remember when you pulled the engine on your last project and took a putty knife to the frame rails to remove the oil layer around the engine and trans? I'm guessing you saw some black, shiny paint. I have used fluid film and chainsaw bar oil with good success. If you don't want it so gooey under there then use wd 40 or similar, but more often. Last year I tried marvel mystery oil in my paint gun. I do these treatments in August, parked in the grass, and afterwards drive down a dry gravel road to seal it. Of course this doesn't count on a show car.

[grumppyoldman]

I live on the Texas gulf coast and we have high humidity with salty air. The car looks to have come from a dry climate and I don't wan't it to rust which i'm afraid it will here in this climate. It's in too good a shape to not do anything. Al