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Old 01-28-07, 09:33 PM   #1
scotthorrigan
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powder coating a painted frame?

there is a frame i'm interested in picking up but not too fond of the color. would I need to strip the frame before I pay to get it powder coated?

I'm assuming the answer is yes, but then again, i don't know anything about powder coating
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Old 01-28-07, 09:48 PM   #2
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yeah. probably should be stripped bare.
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Old 01-28-07, 09:51 PM   #3
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Must be stripped bare. Powder is electristatically applied, and basically melts into the pores of the metal when it's baked. Even if you got enough to hang around over small areas of paint, it wouldn't adhere and would chip off very quickly. Plus there's a chance that the any remaining paint could bubble in the oven.
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Old 01-28-07, 10:15 PM   #4
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Stripping the old paint is necessary as twahl says. Lots of places that do powdercoating have stripping capability, either by sand- or bead-blasting, or by chemical dipping.

This differs from wet paint, for which the original factory-paint can form a very good primer or base coat (esp. if you sand it down smooth).
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Old 01-28-07, 11:18 PM   #5
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Quote:
Originally Posted by scotthorrigan
there is a frame i'm interested in picking up but not too fond of the color. would I need to strip the frame before I pay to get it powder coated?

I'm assuming the answer is yes, but then again, i don't know anything about powder coating
Powdercoating companies will typically sandblast it for you. If they don't do this, ask them to. Save yourself the trouble. I paid $75 for a sandblast and powdercoat.
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Old 01-29-07, 06:58 AM   #6
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You don't want to sandblast thin tubing particularly aluminum. Heavy abrasive blasting can damage the base material. This is a real concern on light weight thin-walled tubing. The preferred method would be "media blast" which would use glass beads or even better - walnut shells. This strips the paint without any damage to the base material.
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Old 01-29-07, 07:02 AM   #7
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Originally Posted by blamp28
You don't want to sandblast thin tubing particularly aluminum. Heavy abrasive blasting can damage the base material. This is a real concern on light weight thin-walled tubing. The preferred method would be "media blast" which would use glass beads or even better - walnut shells. This strips the paint without any damage to the base material.
This is true with aluminum because it's a softer metal, and with very thin-walled steel because it's very thin. But most steel, including nice 531 (and the like) butted tubing, is fine with careful sandblasting. This is where it matters whether the place has experience stripping and powdercoating bicycles.

Btw, I paid $90 for sandblast+paint.
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Old 01-29-07, 08:18 AM   #8
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thanks for the help guys.
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Old 01-29-07, 08:48 AM   #9
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Go to a powder coater who does hotrods or motorcycles. The one I use will sand blast the frame if I clean it or not. He wants to make sure there is no oil from your fingers on the frame. If there were places you touched the frame when the powder was baked to give it it's color you would have bare spots. This is a not very good picture of a 1974 Schwinn World Voyager that I had powder coated 10 years ago. I took off all the parts of the bike and the powder coater taped the chromed stay and fork tips. He bead blasted and powder coated the frame and I got it back 1 week later. That was more than 10 years ago and the picture is from last summer. Roger
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Old 01-29-07, 07:05 PM   #10
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Most good powdercoaters will include media blasting in their price quote. The guy I use will media blast and chemical dip the frame before going to powder to insure proper adhesion. Most places charge $100 to $125 for a bike frame and fork.
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Old 01-29-07, 09:32 PM   #11
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Quote:
Originally Posted by timcupery
This is true with aluminum because it's a softer metal, and with very thin-walled steel because it's very thin. But most steel, including nice 531 (and the like) butted tubing, is fine with careful sandblasting. This is where it matters whether the place has experience stripping and powdercoating bicycles.

Btw, I paid $90 for sandblast+paint.
I think the key phrase in tims post here is "experience". The place i went to has experience dealing with bicycle frames. You're taking a risk if you're the first frame they've ever done.
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