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Surface rust -- How to proctect it? (under car)


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I have a car who looks it has bare metal under, it looks like surface rust, not holes etc

But how do you best protect it?

How do you guys do ?

I could buy some cans of under coating (like some tar oil) but would that not lock it in and encapsulate it and rust grows wild beneath it ?

I was thinking to spay it with WD40 so it can still breath but then maybe dust builds up and you have a pancake layer ?

Please advice

What is my best option ?

See picture ......

rocket pans look solid and have the went open like it should be ....

frame has the same problem ie bare metal no paint on it .....

 

IMG_3106.JPG

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I asked this question a while back ofdifferent forum members who had original or preservation class cars that they didn't want to refinish, even underneath. Preservation class is basically what my '61 Mercury is, and I have surface rust on the frame and bottom sides of the inner fender wells and floor panels, but no rust through. I've had different answers  - ranging from doing nothing other than keeping the car out of wet weather and off salty roads to putting different products on that are designed for this purpose.

 

What I ended up doing was spraying on a product called Fluid Film. It's an oil based spray that goes on very thick and doesn't tend to drip off (though it can be wiped off.) It gets decent reviews. I opted for this because I felt the oil in the product would help mitigate (though not remove) the existing rust on the surface. There were other products that have received good reviews that were less oily (more waxy) but I felt that they would essentially be a coating over the existing rust, and if moisture gets between the  coating and the surface rust, that may not be so good.

 

Of course, as you say, the oil will attract dust and dirt. That may not be so good for folks who store their cars in buildings that are accessed by dirt or gravel roads. That's not my situation, so I used the Fluid Film. So far I haven't seen a collection of much dirt/dust on the surface. I did cover my tires before spraying the product on, but you may want to remove the tires when spraying. (Be careful of the brakes.) So far, so good. Like I say, it doesn't drip off on the garage floor like wd 40 probably will, and it tends to stay somewhat thick on the surface. They say you need to do it once a year or so, depending on how much you use your car.

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Why do you want to protect rust? That's not the way it came from the factory.  If you want to preserve it clear coat with a non glossy finish. If it's driven regularly you'll need some protection. 

Terry

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James' product sounds viable, but if its surface rust on an hpof car I would think removing it would be better than preserving? If you are just trying to stop the process from going any further and not concerned about the look of a rusty floor pan, I would give the POR products a chance. I believe that is exactly what they are intended for. I have used a similar product called 'chassis saver' on a piece of construction equipment. I scraped off the loose rust and put that on top. Paint is still there 10 yrs later but it has started to rust again. BUT, this thing is exposed to the elements 24/7.

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I had an old pickup truck when I lived in Maine for towing the Ford T and for plowing in the winter. Plowing is one of the most abusive things that you can do with a truck, and driving in very slushy salt was just as hard on everything. There were garages that would spray the bottom of your car with used motor oil at one time but the EPA sorta put an end to it around the time Fluid Film Came out. I had that truck done every other year and it was still pretty solid at 20 years old when I bought a new truck and moved south. It’s a good product so long as it gets redone every so often but should last a very long time on any of our collectible cars...
 

The rest of the story is that I worked for a major supplier of snow and ice equipment in a manufacturing engineering capacity and not getting to work on snowy days was not very acceptable, we even had a few good jokes about it...

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Regarding used motor oil, I grew up on a farm and my dad used old motor oil to all kinds of purpose, like preserving old agriculture machines like plows for next season, he sprayed oil on the bare metal but as I said before dust and dirt got attached to it as well so I do not know if it is worth the trade off .....?

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When I first bought my 72 Cutlass "S" it had a lot of surface rust underneath! I sanded it down, coated it with rust converter, painted it with Rustoleum Flat Black, and now the secret ingredient......:Old Car Touchless Acrylic Coating" , an "As seen on TV" product from the 90's.It was a liquid that came with an applicator sponge and could seep into every nook and cranny. The product was a disaster on topside paint and turned your car into a zebra when exposed to sunlight, but when used to detail the surfaces beneath it was beyond compare. You couldn't remove it with a blowtorch. The underside of my Cutlass still looks brand new after 25 years since having done this ! KMart liquidated the entire stock of it and I bought the last eight bottles, but I never had to use it again.

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Can you paint over Ospho?
Before applying, use a wire brush or wire wheel to remove loose paint, rust scales, dirt, oil, and anything else accumulated on the surface. After doing this, apply a coat of Ospho and let it dry (overnight). Once the surface is dry, you can paint over it.
 
What does Ospho do to rust?
When applied to rusted surfaces, OSPHO causes iron oxide (rust) to chemically change to iron phosphate - an inert, hard substance that turns the metal black. Where rust is exceedingly heavy, two coats of OSPHO may be necessary to thoroughly penetrate and blacken the surface to be painted.
 
 

Rust  Ospho.jpg

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2 hours ago, MrY said:

Regarding used motor oil, I grew up on a farm and my dad used old motor oil to all kinds of purpose, like preserving old agriculture machines like plows for next season, he sprayed oil on the bare metal but as I said before dust and dirt got attached to it as well so I do not know if it is worth the trade off .....?


Hard to say but on each original Model T I’ve worked on (And my model A) the metal underneath the oil soaked grime was always like new whereas the area that didn’t have that layer were usually pitted... just saying. 

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Hi again .... I never heard of Fluid Film before
So I did a search for it and found a youtube video test about under coating for cars or metal
Flex Seal I would think would be worst ever but in came in as 2nd place
I wish they had tested OSPHO as well but they did not .....
Motor oil was WORST even made the rust more
 

 

Fluid Film test result.JPG

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Get busy and start sanding - then coat with like Rustolium Rust Reformer Primer - https://www.homedepot.com/p/Rust-Oleum-Automotive-10-25-oz-Rust-Reformer-Flat-Black-Spray-Paint-248658/202623091 or ... (lots of products to choose from) - but nothing desirable about a rusty car underneath even doing a preservation car for AACA. 

Edited by John_Mereness (see edit history)
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I've had experience with some of these products other than Fluid Film, too. Some observations:

 

Flex Seal - There are two different application methods for Flex Seal - spray on and brush on - and the different application versions are different enough in final result as to almost being completely different products.  The spray on version probably protects better than the brush on version, BUT it remains tacky almost indefinitely. Attracts dirt, therefore.  Never seems to completely dry. The brush on version completely dries to a nice semi-gloss sheen, but it will peel off pretty easily after a while (a few days...at least in my experience.) I think this is better suited for putting a coating on plier or tool handles than automotive surfaces.

 

POR 15 - A legendary product that's even positively reviewed by Jay Leno, but you have to apply it in the right context AND it requires a lot of prep work for it to last like it's designed to. Some of the old school "sand-blasting-is-the-only-way-to-get-rid-of-rust" guys look down on POR 15, but I think many of them haven't tried it. It's an encapsulater that is rock/steel hard when dry. The paste version "Patch" can also be used as an adhesive - (Not as strong as 3M panel adhesive, but pretty strong and should be adequate if used in conjunction with other methods of attaching, like fasteners, welding or rivets.) My "right context" comment means it'll work for many old car rust applications that aren't going to see a lot of harsh use or rain/snow/salt. It will last indefinitely if you use it on your Model A that got some surface rust on floorboards due to leaky windows. But on an old 4WD or Jeep that gets thrashed in the Pacific NW, maybe not so much.

 

Just started using some Rustoleum Rust Reformer as a cheap and easy alternative to POR 15. Looks promising, but I haven't had enough experience with it. You need to top coat it. The CRC version of this rust encapsulating stuff is something I've also used, and it's okay, but probably not going to last as long as I wanted in the long run, which is why I tried the Rust Reformer. (This ISN'T the oil based CRC product in the review. No experience with that. ) The CRC stuff also needs a top coat, and I also used a primer on it.

 

All of the products I've mentioned are essentially paints and coverings, and some people with all original finishes aren't going to like them.

 

 

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