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I recently painted an aluminum bike. I put the primer down, then the paint color, then a clear coat. I did all the sanding and everything that goes along with painting the bike. After letting it dry for appox a week after finishing the paint, I clamped it down on the bike stand. When I took the frame off the stand the clamp and dug into the paint. Anyone know why this is happening and how I can fix it so it doesn't continue to happen??

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Soft paint and a hard clamp. Paint often takes weeks to fully harden, and sometimes paint (or, more significantly, varnish) will not fully harden at all, because the humidity was too high when it was applied. – Daniel R Hicks Aug 22 '12 at 20:46
Aluminum is difficult to paint effectively. One recommendation is to purchase the same brand/series of primer/paint/clear coat so that they're specifically designed to be used together. – WTHarper Aug 22 '12 at 21:23
Lots of people also recommend stripping the frame of ALL paint with a chemical stripper and then using a metal etching primer to increase adhesion. Sanding between coats of primer and paint with 600 grit wet/dry paper is also a good idea. – WTHarper Aug 22 '12 at 21:31
If the weather has been humid the paint will take longer to fully harden. Did the clamp did have some rubber padding on it ? – mikes Aug 23 '12 at 1:39

1 Answer

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I'm no expert but having repaired the paint on several cars, I would think that a week from the application of the last coat should be long enough for the paint to cure if it was applied correctly. That said I would assume one of two things:

  • You are clamping the frame much to tightly. I had this problem when I first bought my stand. Buying a carbon bike cured me.
  • The application of the paint was too hasty. Possibly the primer or one of the early coats of paint did not have time to cure and adhere as it should. This would allow subsequent layers to shift when pressure is applied.
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A week is nowhere near long enough for many paints to fully harden. – Daniel R Hicks Aug 22 '12 at 21:48
Thanks for the info. I'm gonna fix it as best I can for now. Once the winter comes and my wife doesn't want to be outside, I'll strip it back down and start over. Thanks a lot for the help. – Steve Aug 22 '12 at 21:52

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