Chassis paint

Vin-tin

Vin-tin

Well-known member
Just picked up my chassis and axles from the blaster guy and flash rust is already starting to show up so I hit these areas with a phosphoric etch / prep product. Hopefully I'll be painting within the next few weeks.

What primer and paint do most of you guys use for the under carriage?
I was thinking of using an epoxy primer, followed by a 2k ceramic chassis paint, but am concerned that the epoxy and phosphoric coating wont get along. Some say it will work, others say no. The more i read, the more confused i get.
Does anyone have experience using these products together? And if so, what brands worked and what didn't?
Or is there alternative products that will work together and still give me a tough chip resistant finish?
 
The phosphoric etch should not have left a coating. Just rinse with water, dry, and immediately prime with epoxy.
 
Epoxy will not cure in the presence of an acid at the surface.

You must be absolutely sure all the acid is gone on the surface before epoxy. What will happen is the epoxy touching the metal will both cure and not bond to the surface.

If you use a 2k paint then you can get a seal on the part and it will bond to the etched surface.

As always you must follow the directions for the etch and all other layers.

Hope that helps.
Keep in mind there are many ways to do the paint right. I have learned epoxy direct to properly etched metal, then the next coat while the epoxy is in the re coat window will result in the best bond.
 
Applied coatings on a rusty chassis over 20 years ago following "all" directions recommended by POR 15.

From what I see 20 years later in an unheated very high humidity area, (lots of moisture collection), it may begin to re-rust maybe a week after Rome rebuilds their Worldwide Empire.

After having years of experience with Rustoleum on Model A trailer axles, this POR 15 coating makes Rustoleum look like one painted his chassis with salt water.

The key is to follow POR 15 exact instructions ..... one coating per three lifetimes should be enough.
 
Try Magnet Paint's "Chassis saver". From those who've used both, it's very similar to POR 15. Google Magnet Paint
Terry
 
We ought to have a little seminar about how to properly etch with Phosphoric acid and the rinsing thereof. I never felt comfortable with my results.
Terry
 
Terry said:
We ought to have a little seminar about how to properly etch with Phosphoric acid and the rinsing thereof. I never felt comfortable with my results.
Terry
Click to expand...
Terry, that's exactly how I feel also. I've used this stuff in the past. I've tried several methods and they all made me wonder about top coating them. I tried applying it with a spray bottle, waiting 15 minutes, and then thoroughly rinsing it. It started to flash rust again before I could get it blow dried. So then I tried using a green scotch pad to rub a light coating onto the metal and let it dry. That keeps the rust away but now I wonder about adhesion problems with whatever I top it with. So far everything I painted seems to be fine. But I never topped the acid etch with any type of automotive primers or top coats. Just hardware store enamels.

From what I read, whatever I use can not contain any type of acid. If the epoxy primer has any type of acid in it, it will react to the phosphorus coating and make me have a very bad day:mad:.

Would I be better off just skipping the epoxy primer and just shoot the 2k chassis black onto the acid etched metal.
 
Kevin in NJ said:
Epoxy will not cure in the presence of an acid at the surface.

You must be absolutely sure all the acid is gone on the surface before epoxy. What will happen is the epoxy touching the metal will both cure and not bond to the surface.

If you use a 2k paint then you can get a seal on the part and it will bond to the etched surface.

As always you must follow the directions for the etch and all other layers.

Hope that helps.
Keep in mind there are many ways to do the paint right. I have learned epoxy direct to properly etched metal, then the next coat while the epoxy is in the re coat window will result in the best bond.
Click to expand...

What is the proper method so epoxy can be used.
 
If applied correctly the acid and the metal should have completed a change into a coating that is no longer acidic. When ready to paint use grease and oil remover as you would in any case and you will be fine.

Like Glenn said"...Rustoleum red primer and semi gloss black top coat. Looks good and is very durable."
 
Vin-tin said:
What is the proper method so epoxy can be used.
Click to expand...

Proper mechanical etching (sanding or sandblasting). Proper wax and grease remover (as per instructions). Paint.

The epoxy adheres to the roughness of the surface and forms a complete moisture (oxygen) barrier.
While the epoxy is in its recoat window, it has tiny holes. So the next coat of paint, which should be a 2 part curing paint or bondo type stuff, will slip it molecules into the holes. As the epoxy cures it will tighten its grip on the paint holding it tight.

As the above was explain to me by the owner of SPI paints. I should also point out that the 2K paints cure to form one large 'molecule' that coats the part.

I will note that SPI paints are a quality lower cost solution to all your under coat paints. My experience with calling for help has been getting the owner on the line and ending up in some technical discussions on how paint works. Of course, I still am terrible at getting paint to lay down nice. Outside helps only goes so far :)
 
Hi Kevin, "Terry, NJ" has a good suggestion with the "Chassis Saver", #UCP970 carried in the NAPA stores. It is indestructible (hard to sand off), offered in Antique Satin Black and a primer is not recommended. Its not cheap (approx. $45.00/quart). It is available with a solvent so it can be sprayed. One other comment, after it sets up, there is no known solvent that will get it off of your hands. Wear gloves! If you get it on your hands, the NAPA store told me to wait a week and let it wear off. I use it on all my under body components.
 
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