Best chassis paint for rusty frame

B

Brianpfreeman

Member
Going to freshen up the coupe frame soon. This is a low budget build project but figured a fresh coat of paint on frame and inside fenders would make it look good. Body is NOT coming off and yes it has surface rust. What is the best paint for chassis/frame components? Looking for good black and something I could brush, roll, or spray.
 
Maybe POR15??? Anytime you have rust, grease, -or anything that would cause the new paint being applied to have adhesion problems, then it is going to cause longevity issues, ...so IMO what you are doing is just making yourself feel good for the moment. Therefore just look towards something that is 'cheap', and not really the 'best' unless both of those words define the same product. Generally from my vantage point, those two words rarely ever describe the same product. ;)
 
Years ago I had a Model A that had a great body and interior but the underside was 50 years of surface rust.

I did not want to take the car apart, it looked to good and ran really great.

I power washed the under side. Removed the rear fenders, and undercoated the car. Put fenders back on using new bolts. Replaced the exhaust. Car looked great. Not a restoration, but a really good 20 footer.

Undercoating still looked good years later when I sold the car.

Enjoy.
 
Undercoating over rust is a very bad idea. I have seen several cars where that was done and it essentially trapped it in and rusted it out. Over treated metal it is OK but rust no.
 
Most is surface rust and nothing really overall bad. Just trying to clean it up a little. This is just a littl jalopy car. Looking for input on Por-15 or if any used Rest oleum farm paint
 
Give the frame a good going over with twisted bristle wire brushes. Treat the frame with phosphoric acid, then apply 3 light coats of POR-15 Chassis Black followed by a top coat of your favorite gloss black enamel within 24 hours after the POR-15.
 

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Brent is spot on. nothing better.

if you want to be cheap, use rustoleum, but it wont last.
 
I am not sure most would agree, but I sent all of my black chassis parts to a powder coating company. This included the frame, axle housings, front end parts, backing plates, steering gear box, rims, etc... I protected the parts that I didn't want to get shot blasted or powder coated. They all were sent dirty and came back done in a CAT black color. It was very reasonable in cost.
 
Bob Bidonde is absolutely correct on all his points. I have done a lot of this kind of work, so let me add to his advice. Clean any residual grease or oil on the frame with generous amounts of mineral spirits (paint thinner) to remove grease and oil with a wire brush. The mineral spirits will dry without leaving any residue if you clean it thoroughly. The phosphoric acid will have no effect on grease/oil and it will still be present if not removed. After you clean off the grease/oil let the mineral spirits dry before proceeding to use the phosphoric acid and the other steps he mentions. Do this and you will be very satisfied with the results.
 
I find the semi scientific tests of products on You-Tube interesting but I'm also a bit skeptical about some of the tests and the individual results. One has a one year exposure test to the elements and one has a test where oxidizer is applies to the surface on two out of three test pieces for each brand. Application of strong oxidizers is generally not how we treat our cars after performing so much maintenance to them but it does show the performance of some of these products if they do get left to the elements. They damn sure all deteriorate but some are worse than others.

I've been using conversion coatings since I got into the aviation maintenance field many years ago so I have my own processes for metal treatment and protective coating application. If corrosion can't be completely removed, a person should do the best they can either by mechanical removal or chemical removal where possible. Surfaces should be treated with a zinc/phosphoric conversion by wetting the surface and keeping it wet for at least 5-minutes to convert iron oxides and to etch the metal for good adhesion. the surface can be rinsed with water or wiped with damp towels that don't leave too much debris behind. The assembly needs to completely dry after treatment and be thoroughly cleaned with wax and grease remover prior to priming. I still use zinc chromate primer but any good quality corrosion preventative primer can be utilized. All this will be followed with any filler materials if a person thinks they need them. The top coat should be the strongest top coat that a person can afford. In the case of a frame, any good quality single stage polyurethane or acrylic urethane can be used.

The key is keeping any further oxidizers from getting to the metal. Either cover the car or keep it in a garage. Ultraviolet radiation from the sun and oxidizers are your worst enemy if the finish is to last any major amount of time at all. Limit sunlight and exposure to moisture as much as practicable. Rinse the car with fresh water if exposed to any oxidizers like winter road salt or salt sea air from that drive along the coast. Even some rainwater can be mildly acidic if a person lives near a lot of industrial manufacturing or say a coal fired power plant.

I've seen powder coat flake right off on parts where the applicator didn't clean or treat the surfaces well enough. It may seal the surface for a longer time but nothing lasts forever in a harsh environment. Powder coating isn't all that practical on some parts due to size and/or complexity of shape or condition. If powder can't get inside something then it can't seal it completely. If it's corroded then is will eventually start to come back and bubble the surface up.
 
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Brian,
Based on your request Rustoleum makes a great low cost product with very good application, adhesion, and durability qualities.
I’ve used several different products including POR 15.........while they all have their place Rustoleum is budget friendly and has good durability.
Degrease your project area, scrub/sand it well, and clean before you paint it. Rustoleum sprays well, brushes out nicely and is durable.
Send a pm if you want to chat-
 
CA Victoria said:
Brian,
Based on your request Rustoleum makes a great low cost product with very good application, adhesion, and durability qualities.
I’ve used several different products including POR 15.........while they all have their place Rustoleum is budget friendly and has good durability.
Degrease your project area, scrub/sand it well, and clean before you paint it. Rustoleum sprays well, brushes out nicely and is durable.
Send a pm if you want to chat-
Click to expand...

Thank you. I plan to scrub/sand and clean it all up. Think I will go this route. Was factory chassis gloss black or a satin black color?
 
I have had very good results with rustoleum on several projects over the years. That paint will darn near stick to anything grease and such included (they make a primer too). The underside of a street vehicle really doesn’t see much abuse, after all although it get wet if the car is driven in the rain (for most Model As that’s not very often) it is not exposed to the elements all that much. What really kills paint is sunlight not water. You have said that you want to go inexpensive so Rustolem is your best bet. I could go on and on but take a look at their products they have “rust reformer” which has phosphate in it and is magical stuff, They have “Rusty Metal Primer” and they have “Clean Metal Primer” have have spoken to their tech support many times about all these products. “Clean Metal Primer” is a bit misleading, that’s the go to primer for most applications including old paint surface rust and even though they wont come out and tell you this it sticks pretty darn good to gunk too. Here’s the beauty of basic rattle can undersides, if a problem area develops, so what? Grab the can and shoot it, big deal. I have an old Willys Jeep that sees use on all kinds of terrain including salt water beaches and that’s what I have used for years and with excellent results. Just my $0.02
 
Whatever you use I would certainly treat with a rust converter such as OSPHO
first. A water consistency converter - not a gel type like naval jelly will get down in all the little cracks and joints. Just read the directions for whichever one you use. Then topcoat with your choice.
 
I have had goos luck spraying on a Rust Converter (the stuff that changes rust to black oxide) then smoothed it out and painted. Seems to last for a long time.

I am not a fan of power coating. Once it is chipped and moisture gets underneath, it done. Not easy to touch up with more powder.
 
The original Rustoleum was successful because it was based in "fish oil." Something about fish oil allows it to penetrate and hold on rust - and the coating deters continued rusting and lifting of the finish.

When I worked at the farm we went through this and the farmer (smart dude) says he uses a product now called "SEM Rust Shield." "It works the same way as the original Rustoleum" he says.

I used it there. Not cheap it's about 3x the cost of a normal quart of Rustoleum. You clean your brushes in alcohol IIRC. It comes in various "standard" colors including gloss black, John Deere green, and a few other.

I've used it on a JD 110 mower deck. I never saw further progression of the rust in the 10 years of use. Grass tends not to adhere to it.

I see from the can in my hand that they have a website www.semproducts.com. Examination of that indicates that theirs is a "system" to include a cleaner/prep before actual coating.

Hope this helps.

Joe K
 
Hello, no matter what paint, I used the POR 15 on my car, the prep work is most important, usually I think people that have issues with any product doesn’t take the time to properly clean and prepare the surface, also my experience POR 15 holds best on wire brushed , metal prepped bare steel. Just paint over loose rust and paint doesn’t work well.
 
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