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Old 10-15-09, 05:58 PM   #1
Cyclesafe
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Urethane Coating vs. Powder Coating

Which is tougher and more solvent resistant?

After 20k miles of touring my frame doesn't look so good. Co-Motion charges a minimum of $350 to repaint my bike with "PPG Global System" paint. San Diego Protective Coatings will paint my frame with "urethane" for much less. Cheaper yet (but not by much) is polyester "powder coating". Nobody seems to be too specific about chemistry and I just can't find anything readable (at least to me) online.

I am most interested in toughness and second in solvent resistance. Can anybody help me? Thanks in advance for your help.
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Old 10-15-09, 06:16 PM   #2
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curious to see what route you go. i've been spray painting because powdercoating looks awful and anything else isnt cost effective.
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Old 10-15-09, 07:28 PM   #3
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Urethane paint is still paint, doesn't have the resistance to scratches and chips as powder coating.

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Urethane paint was first created in the mid-1960s, utilizing the newly-developed plastics technology of that era, to be superior to enamel paint in terms of durability. It also has the advantage of being a surface that can be applied over enamel if the enamel-painted surface is prepared first. Urethane painted surfaces are minimally affected by ultraviolet rays, making the paint a good choice for outdoor surfaces. It is widely used in the automotive industry because of its durability.
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Old 10-16-09, 09:52 AM   #4
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I used to be an engineer for a company making water treatment plants and equipment for flue gas desulphurization in power plants. We used 2 and 3 component urethane epoxies for painting most of this equipment. It is very durable and especially resistant to solvents, acids, caustics, uv, etc. It does require specific preparation and application. Most of the paints we used were only available to commercial customers, but you, as a consumer, you might be able to get useful information from a Sherwin Williams paint store. Just ask them about their industrial epoxy line.
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Old 10-16-09, 11:06 AM   #5
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Aren't the Dupont Emron and Centari (sp?) paints urethane based?
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Old 10-16-09, 04:19 PM   #6
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A properly applied urethane paint job typically has superior appearance to powder coat (more gloss and the ability to clear over graphics) but only about 80% of the toughness. If you are not picky about appearance, I’d go for the powder coat – get epoxy powder since its more durable than polyester.
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Old 10-16-09, 05:11 PM   #7
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Aren't the Dupont Emron and Centari (sp?) paints urethane based?
Yes, they are polyurethane paints. However, Imron is banned in many areas with low-VOC regulations. Not to mention the cyanide content requiring higher-levels of OSHA-compliant forced-air respiration.

Personally I like the colouring-options you have with polyurethane paints over powder-coating. The finish is also much glossier and makes powder-coating look like a rattle-can paint-job. But if you want scratch-resistance and don't care about colour variations, then powder-coating is the way to go. It's not bulletproof tough, it'll still scratch and chip just like any other paint, just that it takes a little more force to do so.
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Old 10-16-09, 06:02 PM   #8
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Yes, they are polyurethane paints. However, Imron is banned in many areas with low-VOC regulations. Not to mention the cyanide content requiring higher-levels of OSHA-compliant forced-air respiration.

Personally I like the colouring-options you have with polyurethane paints over powder-coating. The finish is also much glossier and makes powder-coating look like a rattle-can paint-job. But if you want scratch-resistance and don't care about colour variations, then powder-coating is the way to go. It's not bulletproof tough, it'll still scratch and chip just like any other paint, just that it takes a little more force to do so.
Imron is a urethane but Centuri was not. The bad stuff in Imron is called isocyanates, it's also in other brands of two part catalyzed urethane paints.

This bike was painted with PPG urethane. Very durable and high gloss.

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Old 10-16-09, 06:14 PM   #9
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Personally, I like the powder coat. There's an incredible range of color (I've found no color variation thus far), it's very, very durable, and when the right guy does it, the gloss is amazing. Decals are an issue, however.
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Old 10-16-09, 06:37 PM   #10
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Just FYI:
There are different types of powder used/sold:
http://www.specialchem4coatings.com/....aspx?id=resin
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Old 10-16-09, 07:21 PM   #11
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OP here. The funny thing is I was trained as a chemist and spent several years selling chemical additives for paint. But despite having this background I find it nearly impossible to find out anything. "Urethane" can mean any of several coatings. Same with "powder coat". I have given my frame up to the vendor who will paint it with "urethane" whatever that turns out to be. He also powdercoats bikes with polyester rather than epoxy because of better weather resistance. He said that "urethane" and his PE powder coat was in the same ballpark regarding toughness, but the former was far better for solvent / degreaser resistance. He also said that the urethane will take longer to cure out and will be about 50% more expensive.

I know its no deal, but for sand blasting the PPG Global Systems (whatever that chemistry is) putting a base coat primer (epoxy?) and then a glossy top coat he's charging for my frame and racks $175.

I'll post of pic of the result. Thanks for your responses.

BTW Sci-Fi great link.

Last edited by Cyclesafe; 10-16-09 at 07:25 PM.
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Old 10-16-09, 08:13 PM   #12
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Where I used to work we salt spray tested several different powder coat formulas. I don't know the specific details but I know the urethane powder had better salt spray durability than polyester. Not saying polyester is bad, just that urethane is better for corrosion, which is typically an issue with steel frames.
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Old 10-16-09, 11:32 PM   #13
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As a second to your decision to skip Comotion, our Co Mo tandem paint is very soft, chips
easily. Looks good but annoyingly soft. 4mm allen wrench dropped 5-6" is enough to ding
it.
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Old 10-17-09, 07:27 AM   #14
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Centari is acrylic enamel.
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Old 10-17-09, 12:27 PM   #15
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Quote:
Originally Posted by illwafer View Post
curious to see what route you go. i've been spray painting because powdercoating looks awful and anything else isnt cost effective.
A good powder coater can make your frame come out as nicely as paint, and it will be more durable as well. And powder coating is less toxic than paint and usually less expensive than paint.
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