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Old March 8th 18, 02:13 AM posted to rec.bicycles.tech
JBeattie
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Posts: 5,870
Default No powder coating for aluminum?

On Wednesday, March 7, 2018 at 4:52:45 PM UTC-8, Frank Krygowski wrote:
Our ancient (1986) Cannondales could use some refinishing. The paint has
bubbled and chipped in places, exposing the aluminum. The bikes aren't
grossly ugly, but they're far from pristine. I think the original paint
is DuPont Imron, or some similar catalyzing paint.

I was given information about a local place that does a good job with
powder coating, and is not very expensive.

But I got to thinking: The bikes are 6061-T6 if I remember right. And I
think powder coating gets baked at a higher temperature than the
aluminum did. I'm finding that T6 heat treatment involves about 350
degrees Fahrenheit, but powder coating uses about 400F. That makes this
sound like a bad idea.

Is there something I'm missing?


From some interweb poster:

"Powdercoating is a process where a power is electrostatically stuck to metal then baked on. The baking procedure is done at around 390°F, the melting temperature for 6061 is 985°F and the annealing temperature for 6061 is 775°F for 2-3 hours. Unless you drastically mess up the cure cycle on powdercoat, you're not going to even touch the temperature where the aluminum structure changes. You might get into a precipitation hardening temperature, but you'd need to hold 320°F for 12 hours or more to see a difference.

Anyway, most every bike manufacturer uses powdercoat on some of their bikes.. If it was detrimental to the structure they certainly wouldn't use it so extensively. Plus, you're getting a bike from a manufacturer so they would be the one liable for the job they do. Annodizing produces a harder surface of metal, but powdercoat does not hurt aluminum in any way I know of."


Who knows if that's right. I've also seen reports and pictures of powder coated Cannondales. People do it.

-- Jay Beattie.
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