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  1. #1
    Steel is real, baby! frpax's Avatar
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    Stripping paint off a carbon frame?

    Not sure if this is the right forum...

    But, does anyone know if an over-the-counter paint stripper will damage a carbon fiber frame? I've used the stuff before on steel and aluminum frames, and it works wonderfully, but I'm concerned about carbon.

  2. #2
    coprolite fietsbob's Avatar
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    why not wet sand whats on there and add another layer of paint?

  3. #3
    Steel is real, baby! frpax's Avatar
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    Quote Originally Posted by fietsbob View Post
    why not wet sand whats on there and add another layer of paint?
    I was thinking about just leaving it raw, with no paint whatsoever. Sanding the paint off is time consuming, and I don't know anyone with a media blaster.

  4. #4
    just another gosling Carbonfiberboy's Avatar
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    I am going to repaint my carbon frame, also, and am thinking the same things. It's not the carbon that might be attacked by chemicals, but rather the epoxy which secures the carbon in the matrix. One can't leave the frame bare for the same reason. UV attacks and degrades epoxy. A clear coat should have UV inhibitors in it. Even simpler to paint it.

    A major question for me is: stealth or no stealth?

    In my case, a Trek factory repaint was a disaster, with paint peeling right down to the carbon, all over the place. So the base coat adhesion is no good and it all has to come off. Not looking forward to sanding it off, but OTOH the coating is not that thick, nor is the paint particularly high quality or hard to sand. It's just a little time and patience. I was told to stop sanding if the surface becomes fuzzy, i.e. now sanding the carbon rather than the epoxy which should be lying on top of it.

    I was also thinking about blasting - glass beads? But I don't know what would be the correct blasting medium. Trek obviously blasts their frames for repaint and just as obviously, they didn't sand after the blasting, which might be the reason for my paint failure. Don't want to spend any time on it, y'know. However that might have been, Trek no longer does repaints, maybe because of the failures.

    My instinct is no paint stripper. Has to have a bad effect on the epoxy.

  5. #5
    Steel is real, baby! frpax's Avatar
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    Good point about bare carbon. I didn't think of that. Then perhaps a matte finish clear coat...

    Still, I'd hate to sand the whole frameset...
    It's not like I'd be leaving the stripper on overnight or anything like that. The stuff I've used before makes the paint bubble up in 5 minutes. Scrape it off with a plastic squeegee of some sort and then wipe it down with some mineral spirits. That can't possibly ruin the epoxy... or can it?

  6. #6
    coprolite fietsbob's Avatar
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    Shop for a bare clear coated Frame, sell the one you just don't like the looks of.

    some one else will ride it without worrying about the aesthetics .. Or look out where you are going instead.

    'clark in hawaii' showed a direct import frame from China without logos. seemed cheap.

    most people pay more for Logos..

  7. #7
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by Ex Pres View Post
    2 parts paints - like Imron - are "epoxy" paints. If you are using a stripper that will remove epoxy paint (like "aircraft" stripper), then I'm guessing it will affect the carbon epoxies as well.
    Actually Imron is a polyurethane, which come in several varieties of chemical resistance. Car paints are acrylic urethanes, which are the softest and most easily removed. Imron a brand of acrylic urethane. Polyester urethanes like Awlgrip are more chemical resistant. Many, but not all undercoaters for urethane topcoats are epoxy based. Which doesn't tell us what a particular manufacturer might have used on their frame, or if it is common practice to even use an undercoater on bike frames. My guess is that it is not except for custom made steel and aluminum frames where corrosion resistance will affect reputation. Mass marketers don't care that much about durability or reputation. A really good paint job is hellish expensive. I believe the factory paint job in our Co-Motion tandem is over an undercoater. The paint job on my Trek is not, as the peeled paint looks the same on bottom and top.

    Applying that logic to the subject at hand, the OP could sand through the paint to the carbon (try 220 dry paper) and see if there's a color change on the way down, especially a change to gray or white, the most common colors of undercoaters. No undercoater, maybe try a bit of remover under the bottom bracket. See what happens and report back. If the black stuff (the carbon/epoxy matrix) is sticky after applying the remover, it'd be sanding time. If it seems clean and dry and unaffected, maybe OK.

    Don't wipe down with paint thinner. Use alcohol. It's better at leaving the surface open for further bonding.

    BTW, I paint boats with Awlgrip professionally, so I know there's no reason except poor workmanship for a well done paint job to ever fail. I never strip urethanes chemically, so I don't know that much about that part of the question, other than I know that some strippers do affect epoxies which is why I haven't used one. OTOH, a boat is a lot easier to sand than a bike frame in terms of square feet/hour.

  8. #8
    coprolite fietsbob's Avatar
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    CF has to be coated with something.. or it deteriorates, looses air worthiness.. Buddy worked on USCG Helicopter blades ,
    they're CF these days.

  9. #9
    Steel is real, baby! frpax's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    Applying that logic to the subject at hand, the OP could sand through the paint to the carbon (try 220 dry paper) and see if there's a color change on the way down, especially a change to gray or white, the most common colors of undercoaters. No undercoater, maybe try a bit of remover under the bottom bracket. See what happens and report back. If the black stuff (the carbon/epoxy matrix) is sticky after applying the remover, it'd be sanding time. If it seems clean and dry and unaffected, maybe OK.
    Sound advice.

    I'm sure there is no undercoat. A good portion of the frame is clearcoated carbon.

  10. #10
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    I can only go by what Kestral's owners sheet for my carbon fork said and they are adamant. "Do not use any paint stripper on your Kestral EMS Composite fork". Emphasis is Kestral's. I take it to mean nearly any paint stripper will damage the epoxy matrix of any carbon composite fork or frame.
    Last edited by HillRider; 10-15-10 at 06:01 PM.

  11. #11
    Senior Member Fissile's Avatar
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    NO!!! DO NOT USE PAINT STRIPPER ON CARBON! NO! NO! NO! The carbon matrix is held together with polymers. Essentially, the carbon fibers are glued together by the polymers. Pain stripper will attack the polymers, potentially weakening, or outright destroying, the part. The way to paint carbon is to lightly wet sand the existing finish. YOU DON'T NEED TO SAND OFF ALL THE OLD PAINT. Repaint with a paint that is compatible with the existing paint, or use a sealing primer, and then repaint with your color/clear coats. Small imperfections can be "feathered" before painting so as not to telegraph through the new paint. If you don't know what I mean by "feathering", go to the library and check-out an auto body painting guide.
    Critical Mass

  12. #12
    Senior Member Shimagnolo's Avatar
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    I would either:

    a) Have the mfgr refinish it.

    b) Have Calfee refinish it: http://www.calfeedesign.com/refinishpricing.htm

    Do *not* use any kinds of chemicals on it.

  13. #13
    Steel is real, baby! frpax's Avatar
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    Quote Originally Posted by Shimagnolo View Post
    I would either:

    a) Have the mfgr refinish it.

    b) Have Calfee refinish it: http://www.calfeedesign.com/refinishpricing.htm

    Do *not* use any kinds of chemicals on it.
    Both a & b are beyond my means. Sandpaper is not.

    So it looks like I'm wet sanding the color off and going with clear coat.

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