Paint question - is this self-etch tractor paint okay for ribs?

[DaveNelms]

41q2+1w-w8L._AC_.jpg

Is there any reason not to use this on my wing aluminum parts? It seems like it would be extra tough.

Thanks!

Dave

[alaskabearhawk]

I’ve never used a single-stage primer other than SEM in a rattle can, but that should be fine.

BTW, welcome to the wonderful world of the great primer debate!

https://youtu.be/cStfQwlJeN0?si=ckNxmJopgjKlHBYO

[DaveNelms]

Thanks!

As far as the debate goes, I live in East Texas where everything corrodes, so I'm pretty well forced to protect all aluminum that has two mating surfaces at the least.

My OCD steps in at that point and says, "That will look like shit. Just paint it all'.

So, it's out of my hands, really.

[geraldmorrissey]

I use Stits EP420 epoxy primer. Expensive and stinky, but tuff. Lots of prep; clean, etch, conversion coat and prime. Gives me a nice warm feeling when I see that beautiful green on my AL parts.

[Redneckmech]

If you live in a corrosive climate it would likely be best to use a two part epoxy primer as it will provide greater protection than a self etching primer will be able to.

Here is the spark-notes version of what I was able to find on the different varieties of primer when I researched the subject:


Etching primer - used primarily as a tie coat to link bare un-sanded steel to topcoat or build primer. It is not a good rust inhibitor, but will prevent flash rust from humidity.

Vinyl wash primer - primer developed for military and marine applications to seal out moisture from steel. This type of primer is extremely durable and water proof. The drawbacks are it's poor adhesion to un-sanded steel, and it's lack of compatibility when used with an underlying tie coat.

Epoxy primer - The most commonly used primer over bare steel or Aluminum. This primer provides very good protection from rust and is very durable. You should use an etching primer tie coat over un-sanded bare steel.

2K Urethane build primer - Contains large amounts of solids to lay down thick coats, and is easy to sand. It is not intended to be placed directly on bare steel, it is a poor rust inhibitor and and it also absorbs water, due to its high solids content. This type of primer should be used over top of an epoxy primer, or a vinyl wash primer before applying finish coat to this primer you should use a sealer.

DTM primers - (Direct-To-Metal) primers are relatively new. They are corrosion resistant urethane primers that can be applied directly to bare sanded steel, and are high build, and do not require a sealer coat. They are a fast curing urethane and are ready to sand within 1 hour. These types of primers do not protect as well as others against corrosion.

Epoxy primer/sealer - this type of primer is used after build primer immediately before top-coating to seal moisture from the build primer. most topcoats are not very corrosion resistant because they are porous and allow oxygen to the metal. This extra step insures that moisture will not de-laminate body fillers, or create lifting of the build primer, or surface oxidation. Most of these primers are the same as regular epoxy primers but will have a different mixing ratio so it is thinner and easier to lay down.

[DaveNelms]

Do you think it would work to use the etching primer on the bare metal then go over that with epoxy?

[jaredyates]

I think this would be worse. If you are going to use the epoxy, follow its instructions. My worry would be whether the tractor paint's etching process is right for aluminum. All of our tractors are steel. Also consider, if it doesn't go well, fixing it sure would be a problem. Considering the whole wing building process, the paint is just one small relatively inexpensive step, but all of the other steps build on top of it.

[Redneckmech]

I helped repair an RV12 that had an unknown etching primer put directly on aluminum without prep. It could be scratched off with a thumbnail. In my experience, the aluminum oxide layer that forms on bare aluminum needs to be removed to allow primer to adhere properly regardless of which primer you use and if you are going to that effort I would be more inclined to stick with a good prep in the form of alodine or prekote and then an epoxy primer since an etching primer would just be adding weight.
I have used the VanSickle etching primer on steel (a dozer) with very good result but chose to use PreKote and EP420 on my wing ribs although Alodine for prep is also a very well proven choice.

[Frank]

I used Stewarts Eko Etch and Eko Prime.
Pros: water based, no odor, fast drying, easy to use, formulated for aluminum
Cons: expensive and not solvent-proof, i.e. needs epoxy top coat in fuel areas

If the tractor paint is solvent-proof, can go on thinly, you can stand the odor and the price is right then why not?

[rodsmith]

I know you are talking about aluminum ribs and I don't think the type of primer used on them is real critical. Just remember, steel parts, including parts inside the wing should get an epoxy primer and top coat. Unfortunately paint like everything else is getting very expensive. During the time I was building, Stewarts top coat went from $225 to over $400 / gallon.

[DaveNelms]

That's just scary.

[Bcone1381]

There is lots of info so far for Dave. My hunch is getting overwhelmed is a risk regarding Primers and he would like advice on the Van Sickle. My guess is scratch builders build with budgets.

https://vansicklepaint.com/documents/van-sickle-self-etching-primer-tds

This is the VanSickle Technical Data Sheet. Dave, I'm giving this a Thumbs Up. If your not money or time sensative, a two part epoxy primer that the Factory uses is really tough. But your choice just seems easy to me. Where the proper breathing and venting equipment.

[DaveNelms]

Thanks!

Now I'm wondering if I can use it on the steel tubing as well and spray the epoxy on top of it.