Squirting Primer and Paint

Stopped by the local paint supply.

His advice is as clear as what you all have put here... and additive.

for the entire project...
-----------------------------
1: suggest re-blasting if possible (not sure this in my cards at the moment, I'll sand a lot of this stuff away, but not sure about a session at the blaster though)
2: use epoxy primer
3: paint with whatever you desire

Additional advice: don't use rattle-can unless you're ding-fixing in a temp way for a proper fix later. (or complete small parts, etc.).

To his admitted detriment, he recommended I powder coat as much as possible (he was a dirt-circle-track sprint-car racer, and PC'd just about everything even though he could have painted it all)... He also recommended the guy I use for doing the powder coating for service, quality, value and reliability...

He gave me a 15 minute lesson on a few other things as well (de-greasers, and such).

My quote for PPG products:
1 gal of epoxy primer
1 gal of med reducer (both paint and primer)
primer hardener (2qts)
1 gal of spruce-tip green
1 qt medium activator
with tax and license out the door, was under $450...
All in all, roughly $100 cheaper than TCP global (they wanted $100 S/H for similar)

I'm not sure yet that I'm clear on the problem that self-etch may have caused me (other than it was a rustoleum product), and that I had project delay that forced me to put it outside in the weather... (and he mentioned epoxy didn't like self etch).

I'll do some more prep work and go visit them again when I'm ready to spray.

Glad I only did the front two fenders at this point.

d

 

i think you could get a good 2k primer and not use epoxy if the self etch is going to be an issue, epoxy is difficult to sand smooth if you are going that route.

 

I won't be using self-etch primers again. I restored a Truimph TR8, media blasting the body to bare steel. I Used Martin Senior self-etch, did the minor fill here and there, and painted it with the same brand basecoat/clearcoat.
Five years later, I have minor rust breaking out in every seam and little lines creeping under the paint.
It turns out, most, if not all self etch paints have talc (talcum powder) in them to make sanding easier. Guess what? Talc absorbs moisture in high humidity areas like where I live. This results in rust formation under the primer.
By the way, the self-etch part of the paint system is the reducer, not the paint/solids component.
Now I only use 2 part epoxy on anything worth doing correctly. As mentioned earlier, I really like the SPI products.
-Donny

 

My experience is limited and old, but i have a big keyboard mouth....

When I worked in the paint shop painting tooling and parts we didn't use acid etch primers on anything but aluminum. What we DID do is shoot straight up acid primer of some sort on aluminum parts to get the primer to stick, then shoot the primer on for the topcoat to adhere to. It was this foul smelling brown stuff.

When I painted my latest CJ, it was made mostly of rust and then the parts I did redo got rusty and the seams were full of rust. It was bad. What i did was wire wheel the whole thing, sand with 80 grit on an angle grinder, and bought a gallon of concrete etch. Concrete etch is phosphoric acid and eats/converts rust. Phosphates it i guess. I think its similar process as parkerizing.

What I did then is actually brushed in the rusty metal rustoleum primer into the seams and all over. Looked like hell, but I wasn't going to paint it for some time. When I was ready to paint it months later, I sanded it with 80 grit on the D/A and shot it with 2k primer then topcoat.

I don't recommend this process unless you like work. One thing is that the rust did NOT come back or peek through from anywhere but a couple spots where the prep work was insufficient.

I actually do not recommend anyone do this. I have now gone with epoxy for this latest iteration.

The price you're getting for material is much better than the price I have paid.

 

This topic has come up many times on the AutoBody101 forums, and the advice is always to use etch primer or to use epoxy primer, not both. Epoxy over etch won't stick. Etch over epoxy is pointless, and possibly prevents bonding to the epoxy.

There are also DTM (direct to metal) primers which apparently have the same acidic character as etch, and will bond well to bare steel. No experience with them.

The hot rod guys all use epoxy. The body shops all use etch, because etch dries fast, and they need to get the jobs done. The neat thing about epoxy is you can apply filler on top of the epoxy within the bonding window, or you can put filler directly on steel and shoot epoxy over it to seal it. Epoxy can be skimmed over, painted with polyester filler-primer, or go direct to top coat, with no concern for compatibility (that's the claim). And you can coat the interior of cavities with epoxy and it requires no top coat. It does harden and require scuffing for recoating after a week or so, and it's not UV stable (except SPI apparently which adds UV stabilizers to their epoxy).

 

Regarding rust in the welded seams, there is a guy on IFSJA that is restoring a Wagoneer from a total rust bucket. Normally it would not be worth the effort, but this is a sentimental project. He floods all the welded seams using a syringe and Hirsch "Miracle Paint." I believe that the Hirsch paint is an MCU (moisture cured urethane) like POR-15 or Rust Bullet or Aluthane.

You need somehow to keep air and moisture out of the back side of the seam. They make seam sealers for this purpose, but the MCU is another approach. The seam sealers are partly cosmetic, meant to smooth the transition between panels.

Re the etch with talc filler that Donny mentions, anything with talc (like bondo) is porous and will absorb moisture from the air. It needs to be completely sealed from the atmosphere or the steel in contact will rust. I suspect what happened was the backside of the seams provided the avenue, and the moisture traveled along the layer of etch.