Painting - rings around the rivets

After my final coat of paint, I have a ring of primer exposed around each rivet head. The topcoat doesn't seem to flow in. Any secrets?

My process is:
1. solvent wipe the part to remove all tape residue etc.
2. Red scotchbrite with Metalprep 79
3. Rinse with H2O
4. Alodine for 5 minutes
5. Rinse with H20
6. Dry two days
7. Two coats Akzo green primer (enough to cover variations in color between aluminum, gel coat and filler)
8. Cure one hour plus
8. 2-3 coats Shopline JTX acrylic urethane direct gloss, 5 minutes between coats

Try thinning/reducting the paint more. Poly's are thick to begin with and the manufacturers are trying to use less solvent in them to keep the fed's off their back. sometimes their thinner recommendations are set not based upon what will work best, but what will meet VOC regs. You may have to adjust your spray technique and possibly add another coat depending upon how much you thin it.

It is the surface tension of the paint that is causing this. Your primer is likely much thinner and therefore a lower surface tension.

EDIT: It is also critical that you use the proper speed reducer. Much of the reducer evaporates before the paint hits that part and a mismatch here can leave the paint too thick. However, you would likely notice other problems as well, like poor flow out or dry spray.

I agree with more reducer. I also primed with AKZO and finished with Acry Glo acrylic urethane. Didn't notice any rings on light colour but when I switched to dark they were obvious. My paint supplier recommended I use 25 to 40% more reducer with my HVLP gun than a conventional gun would require. Also changed from a 1.5mm to a 1.3mm tip and I think this improved atomization. My FLG4 gun also called for 23 psi max at the gun but I bumped this up to 28. Used a medium reducer with booth temp around 70 to 75.

Bottom line - no more rings.

Tip size has limited bearing on atomization, it's really only air pressure and pattern settting. Yes, low pressure and high flow will reduce atomization, but it is really about not over taking the air volume available. Better atomization will help with paint application, but won't help with the surface tension problem though. Paint needs further reducing.

tdk said:

After my final coat of paint, I have a ring of primer exposed around each rivet head. The topcoat doesn't seem to flow in. Any secrets?

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On my RV-6A (painted wih Imron auto system, as I recall), I ended up having to paint the rivet lines with high build primer, and sand off the high build. The high build remaining in the dimple of the dimpled rivets filled just enough of the dimple-rivet gap to get the regular primer coat and then top coat to flow and cover properly.

I had no similar problem when I painted my RV-10 with the automotive PPG paing sytem (polyurethane).

Ring around rivets

I just finished painting my RV7 and I notice this ring phenomin right away, so I smeared every rivet with glazing compound. Not every but all the rivets on top of wings tail and fuselage sides. Swiped it almost completely off. Then sanded lightly before cleaning and priming. I left only a ring of glaze on the rivet. You can still see the rivets. Made paint job look better. I think the problem was air pressure and the wind speed. I used nozzle pressure of 10 or input pressure of 25. My gun drops 15 psi. But paint didn't go around that little rivet crack very well. Oh I used single stage poly urethane. It was very subtle. Normal people wouldnt notice , but you builders will.

Did you wet sand the primer to get it flat and smooth before paint?