Bare metal epoxy primer for truck frame

[crashz]

All good advice. The oily undercoating works wonders but is insanely messy. I installed a trailer hitch on my truck yesterday and was covered in black oil from the NH undercoating. Just from putting the hitch in the receiver and pinning it!

I think the primer and paint is a good thing after blasting the frame, but the protection will come from regular oil undercoating. And if the truck is mostly used in the summer, you'll probably only need to do that once every other year or so. Its easy.

 

[crashz]

Snobbds - nice trucks!

 

[Hay Dude]

Sounds like Fluid Film is the way to go, but I’m getting ahead of myself. Still have a lot of work to do.

 

[ray66v]

If I use the Rust Kutter, or Ospho, would that lessen the need for a hardened primer?

I think the Rust Kutter not only changes rust to iron phosphate, but it prepares the metal for the next coat to bond to it.

Again, the only real reason for a "hardened primer" here, would be to allow it to bond on a molecular level, to the top coat. Which, would also have to be a product with hardener.

The issocyanate molecules in the hardener link up and bond them together.

Not necessary, or cost effective on a truck frame. Unless it's a show truck.

Products like Ospho work well, but requires rinsing, 24 hours waiting time, and some tedious cleaning of the powdery residue after application. That's why I go with the wash primer. Spray it on, wait 30 minutes, start priming. Even lacquer primer bonds extremely well with wash primer under it.

 

[Topzide]

Check out Black Star at www.mrochem.com. might work for what you need. Have used on truck frame rust with great sucess.

 

[dstig1]

The term "epoxy Primer" is used more for marketing purposes. It's got to be good if it has "epoxy" in it right?

Technically, any primer with hardener is an epoxy primer.

Well, no, that is not true. While I know you have a background in autobody repair, this statement is not correct. Epoxy is a specific class of materials/chemicals that cures and crosslinks, typically by reacting with a diamine or dianhydride. There are other materials that crosslink including 2-component urethanes and the alkyd enamels that can be crosslinked with isocyanates, as you also noted. But just because a material crosslinks, does not make it an epoxy.

Note: None of this says whether or not you should use it, just trying to keep terms straight for everyone.

 

[Hay Dude]

Again, the only real reason for a "hardened primer" here, would be to allow it to bond on a molecular level, to the top coat. Which, would also have to be a product with hardener.

The issocyanate molecules in the hardener link up and bond them together.

Not necessary, or cost effective on a truck frame. Unless it's a show truck.

Products like Ospho work well, but requires rinsing, 24 hours waiting time, and some tedious cleaning of the powdery residue after application. That's why I go with the wash primer. Spray it on, wait 30 minutes, start priming. Even lacquer primer bonds extremely well with wash primer under it.

Thanks for the advice. My truck frame is moderately rusted. Has some flaking and some rust jacking, but not enough to require replacement. I want to make sure I convert the rust before painting, right?
I ask sincerely, because I don’t want to skip a necessary step.

Not a show truck by any means, but want to make sure I’ve done as much rust preventative measures as possible before painting.

I like the wash primer idea, but does it convert rust, or just cover it?

Just to reiterate before we drift to other areas, I am trying to restore a badly surface rusted, flaking double truck frame. Trying to make it last 5-10 years if possible.

Step 1 was to remove the dump body. That is done.
Here’s what I’ve got:

I think the next logical step is to sandblast all the loose material and surface rust/flaking off as possible.

I guess my most basic question is: What is the next step I do after I sandblast?

My guess is a rust converter, but that’s where I am looking for suggestions.

Thanks to all and appreciate all thoughts.

 

[ray66v]

I am certified on a number of automotive manufacturers paint systems. NONE of them have, use, require or recommend a rust converter in their best practices. That should tell you something.

If you are not going to properly clean the metal for paint, it's a waste of time painting it. Rust converter is a gimmick for homeowners to use when they can't, or won't properly prepare the metal. If you remove the rust, there is nothing to convert.

Preparing that frame for paint while it's on the truck will be all but impossible.

The rust needs oxygen to form. If you cover the metal with anything that blocks the air and water from it, it's going to prevent corrosion.

I suggest you scrape and wire wheel it thoroughly, them apply a coat of a professional quality undercoating: Rusfree ruberized undercoating, which you can brush, or spray on, https://a.co/d/7hjbILp That will actually do more to protect it than anything you can do yourself. While it's a dirty job, it's very cost effective. It does dry enough to touch it without transfer, but will never crack, or flake off if the surface is clean when applied.

 

[ray66v]

Well, no, that is not true. While I know you have a background in autobody repair, this statement is not correct. Epoxy is a specific class of materials/chemicals that cures and crosslinks, typically by reacting with a diamine or dianhydride. There are other materials that crosslink including 2-component urethanes and the alkyd enamels that can be crosslinked with isocyanates, as you also noted. But just because a material crosslinks, does not make it an epoxy.

Note: None of this says whether or not you should use it, just trying to keep terms straight for everyone.

The Chemists I have worked directly with in product development, and testing consider them all the same, and don't classify the primers with or without, in different categories. They say the "epoxy" aspect as a marketing gimmick, and it's all the same.

If "epoxy" primers were truly better, they wouldn't be making them without it. Most don't have it, regaurdless of cost.

I can further tell you I have used all sorts of products, in every possible application, over decades, and have found no discernible difference between products that use the term "epoxy" on the label and those that don't. They apply, and react exactly the same way.

 

[nova3930]

Tagging for further info. I'm in the process of refurbing my big equipment trailer. Want to paint it with something better than alkyd enamel that every box store has.....

Planning to wire brush and soda blast as much as possible then Corroseal just to cover what little bit might be left prior to prime and paint....