VCCA Home Forums TECHNICAL - GENERAL Body - Sheet Metal, Paint & Wood orange peel with DP epoxy primer

I'm using PPG DPLF epoxy primer on my bead blasted body, and have run into some problems with orange peel. I sprayed the frame with no problems, using the 1.3 mm tip on a DeVilbiss Finishline HVLP gun. Since the epoxy primer is so thick and the specs call for tip sizes between 1.4 and 1.6, I decided to try a larger tip when doing the body. The only larger tip I have is 1.8 mm. Could having too large a tip cause this problem? If so, I think I'll just go back to the smaller tip.
How do I deal with the orange peel? I understand that epoxy primer is almost impossible to sand because it clogs the paper. I'll be using a corrosion resistant primer over the epoxy primer (PPG NCP270). Can I sand the high spots on the primer and continue? Or do I need to take the epoxy primer down to a smooth surface? Thanks.

HVLP guns are very prone to orange peel. The viscosity of the paint mix, air pressure are both critical to a good laydown. I would suggest thinning the epoxy primer and using the smaller tip in the future.

If the orange peel is not too severe then the additional primers with sanding likely will be your best option. Or you can wet sand the epoxy which will minimize the clogging of the sand paper. Make sure to use wet/dry paper. Adding a little dish soap to the water will help. If you have hard water it will be necessary to blow it dry or rinse with soft water to keep mineral deposits from causing later problems.

Thanks. The orange peel isn't too bad, so I think the additional high-build primer with sanding will take care of it. Since this is my first paint job, I think I'll experiment a little with wet sanding the epoxy to see how it goes. How long do you suggest I wait before trying to sand the epoxy? It was just sprayed today. What grit? 180?

Randy,
I sand DP all the time. If you're going to use a surfacer 180 or 220 would be fine. Just don't hit bare metal or you'll lose the advavtage of DP's "moisture sealing".I let the DP set for at least a day before sanding. It does clog the paper pretty fast, so have a lot on hand. It seems that once you break the "gummy surface" of the primer, it sands easier, sorta like plastic filler.
I even use DP as a sort of surfacer on rough parts that I don't want to use a surfacer on that will see a little "rougher use" like fender brackets and license,taillight brackets. I first spray on two coats of DP, sand to bare metal again with 80 leaving the DP in pits or low spots, two more coats of DP, sand with 180 or 220 till some bare metal shows through again, and then finally two more coats of DP and wet sand carefully with 400 so as not to reveal any bare metal. Then topcoat.
It seems to work out well and is a little more "chip resistant".
I usually use a 1.4 to spray the DP with. If you have orange peal problems, try increasing the air pressure at the gun just a little, a couple of pounds or so. I've also added a little reducer to it,like Chipper says,not much, maybe a 1/2 part.

Bob

Thanks, Bob. It's good to know I can correct these errors. I'm sure I'll make a few more before I'm done. I'm not sure there's a 1.4 available for my gun. I think the choices are 1.3 or 1.5. I'm really on the edge of what my borrowed 110v compressor can put out (rated at 10cfm@90psi). By the time I'm ready to paint the base coat, I hope to have a more substantial 220v compressor that puts out more cfm. My guess is that part of my problem is the variability in the air flow with the undersized compressor.

Hi Randy,
One of the biggest causes of orange peel is the paint not thinned enough for it to flow out. Also if you are using thinner what is its dry rate. If it is a fast dry thinner it will dry to fast before it gets a chance to flow out.
John

DP epoxy can use an optional reducer (DTV). I didn't use this, as the PPG distributor didn't think I would need it. I may need to get some and use the minimal amount. There are two catalysts available The one I used has a 30 min. dry time. The other has a 60 min dry time.

As the orange peel wasn't too bad, I was able to take a lot of it down with a scotchbrite pad. Since it's only been a day since application, this was a pretty quick operation.

Randy,
I always reduce the DP with DT reducer when I use my small "touch-up" gun. With only a 1.0 tip it just doesn't spray good straight.
I like to use the 401 catalyst which is the slower one. A little more time consuming since you have to allow for a 30 minute "induction time" after mixing before spraying but it's got a 72 hour pot life which I really like. I can mix some up and then keep it in a sealed can to use over a two to three day period. That stuff is so expensive I hate to waste any.

Bob

Since I already bought the 402 catalyst I guess I'll be using it. But I did buy a can of DT reducer. I went back to the 1.3 tip today and it seemed to work fine, so I didn't reduce it. Tomorrow I'll be doing the fenders and I'll try some reducer 2:1:1/2 just to see what difference it makes.
I also found out about moisture today. I thought I was fine with a good drier in the line, but I was amazed at how much moisture built up between the drier and the gun. I've added a disposable filter on the input to the gun, and that seems to have taken care of it.