Primer compatibility

Anyone know if the Rustoleum automotive rattle can primer will work under PPG single stage epoxy automotive paint. I have a couple of small access panels to paint and would prefer not to have to break out all the PPG primer base and hardener and spray gun etc. as I already have the PPG single stage paint in a aerosol container.
Figs

Primer

Don't know but I would test it after fully cured to be certain. You might use a self etch primer like SEM or NAPA 7220. Both available at most Auto Parts.

Whatever you get, don't get Rustoleum professional series primer in the link below. I got two cans and they are junk. It never cured and after two weeks, I could wipe it all clean with acetone which was a good thing since it would come off easy.

The one that has tested really good is the Rustoleum Aluminum primer in the same 15oz spray can but they are hard to find.

https://www.homedepot.com/p/Rust-Oleum-Professional-15-oz-Flat-Gray-Primer-Spray-7582838/100670373

Bavafa said:

Whatever you get, don't get Rustoleum professional series primer in the link below. I got two cans and they are junk. It never cured and after two weeks, I could wipe it all clean with acetone which was a good thing since it would come off easy.

The one that has tested really good is the Rustoleum Aluminum primer in the same 15oz spray can but they are hard to find.

https://www.homedepot.com/p/Rust-Oleum-Professional-15-oz-Flat-Gray-Primer-Spray-7582838/100670373

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I sent an email to Rustoleum tech support asking if their Self-Etching primer (#249322) or Professional Aluminum Primer (#254170) would be best for 2024 Alclad. Here’s their answer:

Aluminum can be a little tough to adhere to. However, both primers would work great adhering to aluminum and would have the same durability to high wear and tear including chemical exposure. Our Self Etching Primer will chemically etch itself to the surface which makes it suitable on other surfaces like fiberglass. But our Aluminum Primer is designed for adhering to aluminum specifically. In this case, either primer would be a good choice and one is not better than the other for sticking to aluminum. We hope this helps.

Of course, this doesn’t answer the original poster’s question about compatibility with PPG paint.

I’ve used spray bomb primer for small touch up areas and have not had a problem. I wouldn’t trust it for anything big.

rv9builder said:

I sent an email to Rustoleum tech support asking if their Self-Etching primer (#249322) or Professional Aluminum Primer (#254170) would be best for 2024 Alclad. Here’s their answer:

Aluminum can be a little tough to adhere to. However, both primers would work great adhering to aluminum and would have the same durability to high wear and tear including chemical exposure. Our Self Etching Primer will chemically etch itself to the surface which makes it suitable on other surfaces like fiberglass. But our Aluminum Primer is designed for adhering to aluminum specifically. In this case, either primer would be a good choice and one is not better than the other for sticking to aluminum. We hope this helps.

Of course, this doesn’t answer the original poster’s question about compatibility with PPG paint.

Click to expand...

Thank you for the additional info. I can attest the Aluminum primer sticks really hard and durable to chemicals.

Most Polyurethane paint systems rely upon chemical bonding, not mechanical, between the primer and the single stage paint coat. They typically give a max time window between THEIR primer application and the top coat application to allow this chemical bond.

The rustoleum primer WILL NOT chemically bond to the PPG S/S paint (no isocyanates in rustoleum paint), so you will need to mechanically abrade the primer for decent bonding.

I am fairly certain that if you call PPG, they will NOT approve the application of their SS paint over rustoleum primer, though they will likely be ok applying their epoxy primer over it, if it is cleaned and scuffed first. They will likely tell you that you can save the extra step, as their primer will adhere better to the aluminum than the rustoleum will.

Most Epoxy primers are now direct to metal approved and many will not allow that primer to be applied over previously applied self-etch primers, as they have found adhesion issues in these cases.

Not saying rustoleum self-etch primer is bad, only that it is not compatible with direct application of P/U S/S paints. You have to decide if potential delamination between the primer and color coat is a problem for the small part you are contemplating. If the parts are well hidden, this may not be a problem for you.

Larry