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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 07-21-09, 07:58 PM   #1
Scout...
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powdercoating AL frame, compromise strength?

ive heard aluminum wheels on cars can be weakened from the heat process of powdercoating, and i was curious to know if anyone has any info for or against that claim? i want to change the color of the bike i just bought, and im unsure if i should just have it painted or p-coated.
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Old 07-22-09, 02:03 AM   #2
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I've never heard that before. Powder coating bakes the finish at approx 375 - 400 deg. If you decide to paint make sure your painter knows how to prep AL. You need a special primer to adhere to AL. Regular auto paint, designed for steel, will eventually blister and come off. http://www.paintcenter.org/rj/jan05h.cfm
http://www.ronjoseph.com/painting-aluminum.htm
http://www.google.com/products?sourc...title&resnum=5

Good luck.
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Old 07-22-09, 03:45 AM   #3
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If your powdercoater knows what they're doing, alloy wheels should never have any chance of warping. Do your research and pick the right guy/shop.
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Old 07-22-09, 03:51 AM   #4
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I had my aluminum H+son rims powder coated locally. I don't think the rims are in any way weakened or at least they haven't shown any signs of weakness yet.

one thing to remember if your a weight weenie is that powder coating will weigh a good bit more than paint, a couple hundred grams maybe.
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Old 07-22-09, 05:55 AM   #5
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Quote:
Originally Posted by cs1 View Post
I've never heard that before. Powder coating bakes the finish at approx 375 - 400 deg. If you decide to paint make sure your painter knows how to prep AL. You need a special primer to adhere to AL. Regular auto paint, designed for steel, will eventually blister and come off. http://www.paintcenter.org/rj/jan05h.cfm
http://www.ronjoseph.com/painting-aluminum.htm
http://www.google.com/products?sourc...title&resnum=5

Good luck.
Did a quick bit of Googling and found that 6061 is prepcipitation heat treated at around 350deg F. So the powder coat baking could indeed effect the strength of the frame.
Info found here.
http://www.metalbashatorium.com/heat..._aluminium.htm
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Old 07-22-09, 08:10 AM   #6
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Yes, depending on the aluminum, the heat cycle can weaken it. I've heard this from a powdercoater who does lots of motorcycle stuff. He said he generally doesn't have a problem doing them once and doesn't turn the oven all the way up, but he generally avoids coating the same wheel multiple times.

Whether it's enough to effect a frame (either the rigidity requirements of a frame), grade of aluminum, or the process used on the aluminum (billet, spun, cast, etc).... I don't know.
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Old 07-22-09, 09:18 AM   #7
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Anodizing is a stronger finish that won't affect tolerances nearly as much as powdercoating.

I'm relatively new to bicycles - why do some many people talk about powdercoating and now anodizing?
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