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I recently bought a brand-new-but-second-hand, straight-out-of-the-box, white 8-spoker in pristine condition, never been used, never even had a tyre fitted... at an ultra-low price (80€: hate me??) and want to have the front rim powdercoated to match. I enquired at a workshop that offered powdercoating if they could match the white and powdercoat my front wheel (well, not mine, the VFR's).

They replied that they were not willing to powdercoat my wheel as it is alumium and will not withstand the high temperatures in the oven while the paint is being baked on. They only work with steel due to this reason. No aluminium or alloys.

This is the first time I have heard of this, none of the threads I've read on VFRD about powdercoating ever questioned whether the heating process could have negative effects on the aluminium rims. Now I'm concerned. Obviously they are not the powdercoating factory, just a bike shop that offers that service as an intermediary... they sand and strip and send the parts off to be powdercoated... so maybe they don't know what they're talking about. Shiz I used to work in a powdercoating factory and we powdercoated aluminium windowframes like nobody's business, but obviously you're not running a 250 kg motorcycle at high speeds on windowframes so no-one's life is in danger there.

I'm sure there are more than enough members here in the know to shed some light on this.

I have found the following:

Heat sensitivity considerations

Often, the metal's sensitivity to heat must also be considered. Even a relatively routine workshop procedure involving heating is complicated by the fact that aluminium, unlike steel, will melt without first glowing red. Forming operations where a blow torch is used therefore require some expertise, because no visual signs reveal how close the material is to melting.

Aluminium also is subject to internal stresses and strains when it is overheated; the tendency of the metal to "creep" under these stresses tends to result in delayed distortions. For example, the warping or cracking of overheated aluminium automobile cylinder heads is commonly observed, sometimes years later, as is the tendency of welded aluminium bicycle frames to gradually twist out of alignment from the stresses of the welding process. Thus, the aerospace industry avoids heat altogether by joining parts with adhesives or mechanical fasteners. Adhesive bonding was used in some bicycle frames in the 1970s, with unfortunate results when the aluminium tubing corroded slightly, loosening the adhesive and collapsing the frame.

Stresses in overheated aluminium can be relieved by heat-treating the parts in an oven and gradually cooling it—in effect annealing the stresses. Yet these parts may still become distorted, so that heat-treating of welded bicycle frames, for instance, can result in a significant fraction becoming misaligned. If the misalignment is not too severe, the cooled parts may be bent into alignment. Of course, if the frame is properly designed for rigidity (see above), that bending will require enormous force.

Aluminium's intolerance to high temperatures has not precluded its use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region; in fact the extremely high thermal conductivity of aluminium prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable lightweight component.

Apparently there are low-temp powdercoating options, I imagine they are more expensive... as low as 50ºC. Whereas the common powdercoating procedure goes up to 200ºC... this has me worrying my front rim may suffer from a stress fracture and come apart when hitting a pothole.

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I don't know for sure, but I did have mine done by a powder coating place. He actually uses a very high heat oven to bake the old material off first, whether it's paint or powder or both in layers, etc.

He seemed very knowledgeable about powder coating and the various materials to which it can and cannot be applied. He doesn't specialize in motorcycle parts, but knows what can be done, and never said there was any possibility to damage the wheel. I can't believe the high temps required to remove the previous colors during the prep process could be any higher than the temps required to set the powder.

Just my opinion...

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I've been running powdercoated rime on my 800 for probably 10 years or more, and have flogged the crap out of them.

High speed, cornering, wheelies, hard braking, two-up touring, bumpy roads, etc.

All I can say is that I've never had an issue.

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I am in actually in the midst of starting a powdercoating business, and I for one can tell you that you should find yourself a new powdercoat shop/person. There is a lot of fear in the market about this particular topic, and a lot of people simply won't take the risk because there have been incidents of cast rims cracking under what is literally tons of force(race cars), and it in turn gets blamed on the heat cycle of the PCing. It's absolute non-sense to think that a wheel that is formed at such high temperatures( my understanding is cast OE wheels form somewhere around 1200*) would be weakened by a 300 degree heat cycle lasting all of 25 minutes or so. Yes, there are alloys out there that this could happen to, but I don't see a cast Honda wheel being one of them. I think a lot of people do not understand the properties behind castings and their inherent flaws and weaknesses and can be very quick to place blame without further investigation.. The ole "it was just fine before" defense, when those cracks could be superficial, and not hurting the structural integrity of the wheel, or they were caused by a sharp impact, improper tire installation, etc. They very well could have already been there and having a bright smooth finish allowed it to be seen after a little torsion transferred the crack to the coating. It could be fatigue cracking showing with age that happened to be observed late.. There are just endless possibilities. Truth is, you are taking a small risk, because there are no scientific facts on the matter, but thousands upon thousands run PC'd cast wheels without trouble. I definitely plan to powdercoat mine, which I guess, in effect, really means I am willing to bet my life on it... Take that for what its worth..

Certainly do your own research on the matter, possibly talk to Honda corporate to see what their exact process and materials are and possibly what they recommend and then even talk to a metallurgist. Call several different PC shops and ask them for their opinion.

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Excellent contributions fellow comrades... very sound arguments... I would like to talk directly to the powdercoating company and bypass the intermediary... don't imagine there are many in this area...

If a Honda cast wheel is manufactured at 1200C then 200C sounds more like the scenario presented in the info I provided in the opening post, more likely to have an anhealling effect, relieving any existing stresses than to cause more... textually it does say "overheating" and relatively 200C compared to 1200C is nowhere near overheating.

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My understanding is that aluminum wheels shouldn't be heated over 400-450 degrees. I have no idea where I heard it or if it's factual, could be an urban legend. The powdercoating guy that I had do mine said that kind of heat won't be an issue with their process. Mine seem to be fine so far, and I'll have to admit I've never heard of an accident due to a wheel breaking.

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That question comes up a lot on all kinds of car and bike forums - here is one answer.

'A word of caution regarding the powder coating of aluminum.

Forged alloy wheels are desirable because they are known to be both strong and lightweight. To achieve these characteristics, they are typically manufactured from 6061-T6 grade aluminum. At some time during the manufacturing process this alloy must undergo a two-step thermal process in order for it to attain the desired mechanical properties, which include high strength and resistance to fatigue. These thermal processing or heat treating steps are known as solution treatment (985°F) and artificial aging (350°F). With forged 6061 aluminum, the artificial aging step requires the material to be held at 350°F for about 8 hours.

The majority of powder coating materials require a cure temperature ranging from 300 to 400°F with a cure time of about 1 hour. Since this overlaps the temperature of the artificial aging step, the powder coating process has the potential to "overage" the aluminum causing embrittlement and reduced fatigue life.

Recent advances in powder coating compounds have brought about lower cure temperatures of 250°F. These new powder coating compounds are more desirable, since they do not impact the prior thermal processing steps for heat treatable alloys such as 6061-T6 aluminum.

When considering powder coating of heat treatable aluminum alloys (6000 and 7000 series), it is always advisable to confirm that the temperature of the part will not exceed 300°F. Ignoring this fact may result in a sudden and unexpected failure of a critical component. A critical failure in a forged alloy wheel could ruin not just one, but possibly the rest of your days.

Before allowing someone to powder coat your forged aluminum wheels, ask them to use a lower cure temperature (250°F) compound and to maintain the temperature below 300°F at all times while they are processing your wheels.'

If you can't find someone who can use the lower temperature you can always go with paint.

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Has anyone ever heard of a standard aluminum bike wheel failing? Not one of the superlight jobbies, but just a standard bike wheel. Just curious because I've never heard of it.

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Even more precise info there, thank you Dale!!!



Has anyone ever heard of a standard aluminum bike wheel failing? Not one of the superlight jobbies, but just a standard bike wheel. Just curious because I've never heard of it.

Me neither!!

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I just did my rear wheel a few weeks ago. I use powders from Columbia coatings. 380-400f for 20 minutes after part reaches temp. The key is to let it cool down slowly. I just shut off the oven and crack the door.

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Auspanol, you are not scaring me in selling you my powdercoated 8 spoker for 10 bucks.

Nice scam attempt, but ain't flying pal

;-)

(Just kidding)

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Mine have been done for 10 years now and not a single problem. I have gone over the rims a few times looking for stress cracks in the coating and never found anything so to me this also means no rim issues as well. And I really beat the tires up at times on some of the roads i have road.

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I just did my rear wheel a few weeks ago. I use powders from Columbia coatings. 380-400f for 20 minutes after part reaches temp. The key is to let it cool down slowly. I just shut off the oven and crack the door.

You did your own??

Auspanol, you are not scaring me in selling you my powdercoated 8 spoker for 10 bucks.

Nice scam attempt, but ain't flying pal

;-)

(Just kidding)

10 bucks?? You ARE kidding... should be free!!!

Naaa yours is black... I want white!!!

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That question comes up a lot on all kinds of car and bike forums - here is one answer.

'A word of caution regarding the powder coating of aluminum.

Forged alloy wheels are desirable because they are known to be both strong and lightweight. To achieve these characteristics, they are typically manufactured from 6061-T6 grade aluminum. At some time during the manufacturing process this alloy must undergo a two-step thermal process in order for it to attain the desired mechanical properties, which include high strength and resistance to fatigue. These thermal processing or heat treating steps are known as solution treatment (985°F) and artificial aging (350°F). With forged 6061 aluminum, the artificial aging step requires the material to be held at 350°F for about 8 hours.

The majority of powder coating materials require a cure temperature ranging from 300 to 400°F with a cure time of about 1 hour. Since this overlaps the temperature of the artificial aging step, the powder coating process has the potential to "overage" the aluminum causing embrittlement and reduced fatigue life.

Recent advances in powder coating compounds have brought about lower cure temperatures of 250°F. These new powder coating compounds are more desirable, since they do not impact the prior thermal processing steps for heat treatable alloys such as 6061-T6 aluminum.

When considering powder coating of heat treatable aluminum alloys (6000 and 7000 series), it is always advisable to confirm that the temperature of the part will not exceed 300°F. Ignoring this fact may result in a sudden and unexpected failure of a critical component. A critical failure in a forged alloy wheel could ruin not just one, but possibly the rest of your days.

Before allowing someone to powder coat your forged aluminum wheels, ask them to use a lower cure temperature (250°F) compound and to maintain the temperature below 300°F at all times while they are processing your wheels.'

If you can't find someone who can use the lower temperature you can always go with paint.

Well stock Honda wheels are cast not forged so perhaps this does not apply.

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One of the big drivers behind the new "Low-temp" (225/250 degrees F) powdercoating is the concern over what the aluminum wheel has for a heat treat. The heat treat cycle from the factory for Honda wheels starts at 325F (IIRC) and goes UP from there. What the big shops are afraid of is going to 400F will pretty much take the heat treat out of the metal. I'm NOT a powdercoater or metallurgist but there is a lot of info on the autocross sites about guys tearing the centers out of powdercoated wheels. Granted, it's under the stress of autcross-but it has happened. My brother works for Hendrick Racing and he says all the alloy stuff gets the low temp powdercoat-just to be sure.

The above my NOT be gospel, it my just be nickle knowledge.

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I just did my rear wheel a few weeks ago. I use powders from Columbia coatings. 380-400f for 20 minutes after part reaches temp. The key is to let it cool down slowly. I just shut off the oven and crack the door.

You did your own??

Yeah, it's actually easier than painting once you have bare metal. It cost me under $5 to do my rear wheel. The gun wasn't that much and I got the oven for free. You'd be surprised how many things you find to do.

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IMAG0337_zpse606268b.jpg

Fireside copper from Prismatic...single heat cycle, no clearcoat...I guess we'll see...

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  • 1 month later...
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Love the white wheels (almost as much as the red :wink: ), and I have one on the back of the Yamaha, but they are a bugger to keep clean.

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I'm planning on repainting my rims this winter.

The original paint has been scratched, chipped and the usual wear and tear,

Not sure yet if I´ll go with the powder o wet paint yet, Haven´t even decided if I´ll go with the stock white color or maybe Gold like subaru's rims.

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I just did my rear wheel a few weeks ago. I use powders from Columbia coatings. 380-400f for 20 minutes after part reaches temp. The key is to let it cool down slowly. I just shut off the oven and crack the door.

I dont know when they temper steel blades its fire and ice, to get the temper, not cooling slowly

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I just did my rear wheel a few weeks ago. I use powders from Columbia coatings. 380-400f for 20 minutes after part reaches temp. The key is to let it cool down slowly. I just shut off the oven and crack the door.

I dont know when they temper steel blades its fire and ice, to get the temper, not cooling slowly

Whens the last time you rode your knife blades? He's not saying the slow cool is to temper the metal. Cooling slowly avoids distortion from cooling too quickly, especially important on something concentric like a wheel, not so much on a knife blade..

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