Can anybody recommend a clear coat that will work for our products?
My partner and I run a composite manufacturing company. We manufacture clear coated carbon fiber parts for luxury and exotic cars.
Lately we have been experiencing some problems with the clear coat we've been using. We've been using Nason's Select clear. I understand you get what you pay for, and since we've been growing in the right direction, its time to use a higher quality clear coat.
So far we've tried Sherwin Williams Dimension DC5010 Spot / Panel clear coat and CC931 off of their high performance line.
Both clear coats have given me some kind of solvent pop. The CC931 with the 90min cure time has given us worse solvent pop than the cheap Nason.
Here is my application. I tried this with both clear coats.
I've tried wet on wet meaning two wet coats one after another with no flash time.
Ive tried wet on wet, waited 10 min, then came back with another wet on wet.
Ive tried two and three flow coats of clear.
Lastly I've tried two medium coats and two flow coats.
Some methods provide less solvent pop than others, but in the end I am left with a finish that needs to be clear coated again.
I don't understand why. I rarely had problems with the Nason brand but we need to reduce the amount of time spent clear coating parts. Thats mostly the reason I wan't to switch.
What I suspect to be the problem is the substrate we are clear coating. Not that its not compatible, but I'm sure we have to take into consideration that the clear coats weren't designed specifically for the substrates we clear.
We clear over polyester resin, (sanded of course) and not automotive paints. I bring that up because I find myself spraying thicker than normal coats to cover any imperfections or fish eyes that form onto the parts. I usually only have to do this on the first and second coat.
Also its good to mention that we need a high build clear coat. We would like to be able to spray our clear coat like the Nason. With the Nason I'd spray 3 - 4 flow coats after tack coats. Not 3 - 4 at a time. But 3 - 4 coats with 10 min flash times.
Here are some samples of our parts.
By the way... Can anybody recommend a clear coat that we could spray on at least 6 mills of? An average coat of clear from the factory is around 2 - 2.5 mills. I understand that custom paint jobs usually get around 4. I'd like to be at 6 - 8. If I have to do this in two sessions with sanding in between I will, but if there is a clear coat out there that allows you to spray on several coats during one session with out solvent popping, I'd like to know about it .
Also, do clear coats that cure quicker than others, (DuPont snap clear, Sherwin Williams HPC15, etc) tend to solvent pop much more than clear coats that take 6 + hours to cure?
From my reading of your statement I feel you have the wrong understanding of the term wet on wet. It is a bit of a misnomer as you should wait for the first coat to actually dry before you apply the second coat. What they are meaning is that you can apply the next coat without a sanding step in between since you are still within the re-coat window. If you want to eliminate solvent pop then avoiding too much film build on each coat is necessary.
What you described would fit the term “coat and a half”. You can do that when you are putting the minimum thickness on in the quickest application time. Using coat and a half you spray a light coat on a panel then immediately spray a full wet coat over the first without waiting for it to flash. This is a Spies Hecker application for speed, but then you are done. No coming along in a half an hour and adding more because you get solvents trapped and end up with solvent pop. You wouldn’t want to do coat and a half if you don’t have a good booth or if you think you will need to cut and buff since there will be minimal film build.
Since you want such a thick coat of clear then I would recommend several paint sessions with full drying and sanding in between or rethink the need for such a thick coating.
S/W has a clear called Finish 1 FC 710 and FC720. They both have a wet on wet limited flash. Great clear for the money. That don't mean you can shoot back to back wet coats. I wait minimum 10-15 minutes between coats and you need the right temp hardener. Sounds like you may be rushing the job. Bob has good advice. Cheers.
speed clears by their nature are more prone to solvent popping. your are not going to have much luck piling that much product on using a clear that was designed for speed.
Really, it is best to apply 2-3 coats, sand and reclear. this is going to give you the best finish. after all you said these were for exotic and luxury cars. trying to bury defects with 6 coats of clear in a row is only gonna come back to haunt you. once all that product dries and shrinks you are likely gonna see those defects again
You are using the completely wrong products, meaning automotive clears. Use woodworking polyesters or UV cured coatings. There are two companies that specialize in this ICA and ILVA. http://www.icaamerica.biz/
Contact these two companies and you're problem will be solved.
The clearcoated wood you see in high end cars is all polyester coated. Acrylic urethane is great stuff but not perfect for all applications.
Solvent pop is almost always caused by applying too much paint too quickly. Use a gun that atomizes well and wait for the paint to flash in between coats.
Thanks for the great help and advice! I spoke to one of the chemists at Sherwin Williams and he suggested that I spray two flow coats and that's it. Each coat within 5 in from each other. He told me that with the 5010 from Sherwin Williams the clear coat works the best when the flow coats are applied back to back. I tried that on about two dozen parts and it seems to work well. Slight solvent pop, but not enough to require another coat of clear. A few panels look like they were about to solvent pop. So I'll be able to sand that down with 1000 - 1500 then polish.
Thanks for the info! We tried looking at other types of coatings and have found that in our experience, automotive clear coats are the way to go since urethane clear coats are naturally UV resistant because of the chemical base. I was told several times by different techs that the UV stabilizers always wear off on polyester materials since polyester is naturally unstable to UV rays.
What I'd like to try is a thicker polyester coating from Duratec to get the final shape and finish, then go over that with clear coat for the UV protection and shine.
Originally Posted by Dennis N. Schmidt
P.s I'll post pictures tomorrow on the final results .