Clear on Carbon Fiber

A

AlpineCoupe

New Member
First off, I am brand new to spraying clear coat/ paint/ anything so I will take any, and all advice.

I make carbon fiber parts and the person I used to clear coat my parts recently retired so it gave me the opportunity to try to learn a new skill. I called and talked to SPI about what clear would be best and they pointed me to using Production Clear and so far I have been really impressed with how well it works for someone that is just getting started. My question is about a part I recently cleared - pictured below - the top of the part came out pretty well (a few pinholes because of the nature of carbon fiber that I will hope to wet sand and polish out). But the back of the part seems to have excessive dry spray, I think? Can some one confirm this? Also, what are my next steps? Sand it flat with 600 and re-clear?

For the sake of giving all the information this was 2 coats of clear - I thought a pretty wet coat at the time but perhaps not..
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Thanks!
Patrick
 
me personally I usually go 4 coats, sand with 400, clear again on carbon parts. The back kind of looks like a lot of micro holes, but its hard to tell in the pics. If that's all you are seeing on the top for pin holes I'd say you produce some really nice carbon parts.

Here is a first round of clear on something I recently had to deal with.
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Thanks! I've been working with carbon for a while now but am just getting started with the clear coating part. The back actually has fewer pinholes than the top (it's made in 2 pieces so the back and top are manufactured at different times), all of the texture is coming from my amateur attempt I think.

Also, thanks for confirming that I can do more than 2 coats. I thought I read at some point that I should just do 2 coats. Do you spray all 4 coats at once, with proper flash time of course?

I think I'm going to sand this flat with 400 and hit it again, but just spray it more wet than before
 
Yes. 4 coats of euro. At 4:1:1. 30 min.

That piece in that picture required 12 coats total. 3 rounds of painting.

4 coats/400- 4 coats/400 - 4 coats and still needs to slightly buff it when I have time. Just a dnib more or less.
 
Sanded and re-cleared. But it looks like I have microbubbles in the finish now. Things are smooth and look way better than before but is there anything I can do about these bubbles? They seem to be on the upper edge.

I also attached a picture of the back to show how much better it looks, thanks for the advice!!
 

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I’m glad this was posted
I have a carbon piece on the way and have no idea about prep.
Is it just a matter of sanding 400 or 600 , clean with IPA and shoot the clear?
 
AlpineCoupe said:
Sanded and re-cleared. But it looks like I have microbubbles in the finish now. Things are smooth and look way better than before but is there anything I can do about these bubbles? They seem to be on the upper edge.

I also attached a picture of the back to show how much better it looks, thanks for the advice!!
Click to expand...

You're not the first, and you won't be the last to ask that question. I can't tell from the picture if that is solvent pop, if it is, it needed more time to flash off. Did you follow the recommended flash time for the Production Clear? If you did, then I would look at either.....(1) you sprayed your first coat to heavy and it didn't flash off completely before your 2nd coat. (2) you have moisture in your air lines.

Tell us how your dry air is set up from the compressor?

I have an interest in this thread like WornOutWelder, I too will be working with carbon fiber on some interior pieces. OJ is the carbon fiber guru since he has worked with it a lot on one of his current projects.
 
I think I did spray too heavy on my first layer this round of clear. I previously had the dry spray issue so I was trying to go heavier... guess it was too much with not enough dry time.

Anything to do to fix the part now?
 
Worn Out Welder said:
I’m glad this was posted
I have a carbon piece on the way and have no idea about prep.
Is it just a matter of sanding 400 or 600 , clean with IPA and shoot the clear?
Click to expand...
Yes... I think it depends a little bit on the piece though. As you saw in OJ's post about his piece there is the potential to have the part end up with a lot of pinhole depending on the resin content in the piece. Hopefully you don't have to deal with that too much.

Otherwise I typically sand my pieces with 400 after they come out of the mold (lightly as to not get into the carbon), properly degrease (just FYI when I talked to SPI they suggested the water based degreaser for carbon parts), then spray the part.
 
AlpineCoupe said:
I think I did spray too heavy on my first layer this round of clear. I previously had the dry spray issue so I was trying to go heavier... guess it was too much with not enough dry time.

Anything to do to fix the part now?
Click to expand...

Sand it out and buff, or sand it out and respray.

Your choice.
 
AlpineCoupe said:
Yes... I think it depends a little bit on the piece though. As you saw in OJ's post about his piece there is the potential to have the part end up with a lot of pinhole depending on the resin content in the piece. Hopefully you don't have to deal with that too much.

Otherwise I typically sand my pieces with 400 after they come out of the mold (lightly as to not get into the carbon), properly degrease (just FYI when I talked to SPI they suggested the water based degreaser for carbon parts), then spray the part.
Click to expand...
Ive played with vacuum infusion on carbon fibre,was difficult to fill the carbon completely.
Will automotive clears fill the voids enough to look good?
Was just a hobby,tried hand layup with epoxy but still was difficult.I gave up.
 
Tungsten said:
Ive played with vacuum infusion on carbon fibre,was difficult to fill the carbon completely.
Will automotive clears fill the voids enough to look good?
Was just a hobby,tried hand layup with epoxy but still was difficult.I gave up.
Click to expand...
I do exclusively vacuum infusion and auto clears can fill the voids enough. I have found that I can get a really good finish on most of my parts with just a couple of coats of production clear, but from time to time they come out needing more coats.

I just wet sanded the part Im working on from this thread, I'll be polishing it later today and post pictures to show the final product.

Other things I've made have come out without pinholes - like these end plates
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You honestly know far more about carbon stuff than I do, but I had to hand lay some carbon on a roof and I used this product to fill in the voids before doing a final clear on the panel when I painted it.

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This is after I rolled on the resin and basically glued it down.
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After it cured, I scuffed the surface up with some 220 just lightly sanded. and sprayed this product with my 2.5 poly gun.

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Then sanded it when I painted the body.

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I've heard good things about the filling properties of the Duratec stuff - I have't tried them myself but your results look great! I think some carbon guys use certain formulas that have the UV inhibitors and then choose not to clear.

Did the Duratec play well with the SPI clears?
 
That carbon fiber part looks impressive. I mentioned this Duratec clear primer around a year ago. It was suggested that this could be used to increase the transparent thickness and save on clear coat, even if no composites are involved. Something like this: base coat, one thin coat of 2k clear, then Duratec, sanding, and then regular application of 2k clear over the Duratec.
 
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