Help - I'm a Hobbyist, Fairly New to SPI Epoxy Primer, and Having Trouble

dfmoeller

New Member
I'm really hoping someone has conquered this problem before and can clue me in. Here are the details:

I'm a retired electrical engineer with a project, a 67 GTO convertible on which I am attempting a frame-off resto. I have been following this forum for a few months and the SPI epoxy primer seems like its a dream. But, I just can't seem to get it to lay correctly. Attached is a picture of my problem. It looks like nibs in the paint. I've seen other posts claiming the same sort of thing is due to shooting the 1st coat too heavy; so I carefully throttled everything back, and I still have this problem. Here are my details

I thought it would be a good idea to try a practice project before spraying parts on the GTO. I've got an old parts washer that needed paint, so I thought great, I'll treat that to a new paint job.

Gun is DeVilbiss Finish Line 4 with 1.5 tip and HVLP aircap (says to shoot at 23 psi in the manual).

I've carefully followed Barry's recommendations for epoxy; 90% fan, 2.5 to 2.75 turns out in flow, at the above 23 psi. Any further in on the flow and nothing seems to come out.

Heat at 75 in the shop. Parts were sandblasted, followed by two apps of wax and grease remover 700 according to the spray and wipe clean method. The
IMG_7548.JPG
finish is a bit rough, but nothing is sitting on the surface.

First coat went on very thin, followed by a thicker coat after about 12 hours. The picture is after the second coat. Even the thin first coat showed some nibs in it.

From what I've read here, I'm putting too much paint on, but I'm at a loss how to throttle back even further. Does anybody else paint with this gun? And does it work? Somebody clue me in; this is awfully expensive and frustrating to keep sanding this paint off!

Doug
 
How long of wait between 700 & epoxy?
What reducer?
Inline air dryer?

These answers will help the pros.
 
I have had the same problem. Since I have gotten an electric mixer that stirs the epoxy and other primers I have not had any trouble, it always lays down smooth. I figured the had crank type mixer wasn’t doing the job. Hope this helps.
 
Two responses here.

First, the 700 was used the night before the epoxy went on. No reducer per Barry's instructions. Was going to use reducer to match gloss level to ecoat, but didn't get that far. Shop air system is an 80 gallon 2 stage 5hp unit distributing 175 psi via a 1" black pipe system (about 50 ft.) with water trapping drains on all tap points, with a water trap integral on the regulator on the wall and a small moisture filter on the gun. I've never seen a drop of water at the business end of the system. However, you never know. How can I tell if water is a problem?

Second, the mixer is something I hadn't thought of. I had been hand stirring until my arm felt like it was falling off, but that could be it. Any recommendations on mixers?
 
This is what I switched to and haven’t had anything more bumps in my epoxy.
 

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i guess it is possible that the pigment clumped together here but you sandblasted the metal and then wiped it down. that my friend is dirt. if you touch sandblasted metal with any kind of rag then its gonna look like that. once you touch it with a rag you will never get the dirt out of it. it will be stuck in the metal. its like trying to get the dust out of a piece of 80 grit sandpaper. the rough surface of the metal just grabs everything. squirt the metal down with w&g remover then blow it dry.
 
I can't help but think that is particles of towels and such. A sandblasted surface is like Velcro. I would bet if you sand it down and reshoot it, it will look much better.

Also I do not see mention of what kind of strainer was used for the product. We use 125 micron for everything but metallics and pearls.
 
At first, I thought BrianC's suggestion about unstirred paint might be it, but then I thought that nibs are much bigger than the strainer that I used (not sure what the size is - just a paint store strainer that I picked up). The thought about freshly sandblasted surfaces picking up lint off the rags used though sounds promising. I will try again tomorrow after sanding and let you know what it looks like. Thanks much for the input.
 
Not sure if this applies in your situation but sometimes when the air hose is old it can breakdown into small pieces from the inside. If it gets past all filters it shows up in whatever you are spraying. Just something to consider. Hope you can find the problem.
 
I love these suggestions! I never would have thought of these suggested problem sources. Please keep them coming. You guys are a huge help.

elwood - great thought but I just replaced that hose about two months ago, so I don't think that's the issue. The lead in hose from the compressor to the pipes was new about 6 to 8 months ago (I haven't had the piping system very long).

El Toro - great question! The answer is there is none on the masking paper hung on the wall to adjust the gun, but there is a small group of nibs next to the painted article. This stuff is on the surface; probably from my cleaning technique as described earlier, and I"m guessing the part shed some lint on the paper next to it. I'll know more later today. I'm going to sand that stuff off and use compressed air to dry as described above. We will see!
 
Agree on it most certainly being dirt. I was told to quickly DA or hand sand any blasted surfaces to knock the bumps down before wiping them, which has worked great. Either that, or don't put a rag do them. Definitely a learning process.
 
Good news. I just shot two coats after DAing the nibs and most of the primer off and cleaning thoroughly, and NO NIBS.

For cleaning after DA, I sprayed 700 and wiped off with a clean LINT-FREE cloth, followed some time later by spraying 710 and drying with air gun. Last step was tacking twice. Seems to have conquered the Nibs!
 
Smart man experimenting first. Said to self today- for new projects, there's only One first time..
 
Good news. I just shot two coats after DAing the nibs and most of the primer off and cleaning thoroughly, and NO NIBS.

For cleaning after DA, I sprayed 700 and wiped off with a clean LINT-FREE cloth, followed some time later by spraying 710 and drying with air gun. Last step was tacking twice. Seems to have conquered the Nibs!


I'm glad things worked out and using the W&G remover is a great idea but I dont think blowing the 710 off with an air gun is what you want to do. If you had any contaminates on the surface the W&GR would have lifted them off the surface and when you blew it dry it would have just re-deposited them. Anytime you use 700 or 710 while it is wet wipe it off with a clean rag. Don't let it dry before you wipe off the contaminates it has lifted up.

Good luck. Glad you are making progress.

John
 
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