I want to take a set of stock '02 Z06 wheels and completely powder coat them flat black. (no polished lip) The wheels would be used for street, autocross, and the occasional track day. I have seen a few people on the forum say that this could weaken the wheel but I really haven't seen anything to back it up. The powder coating shops I've talked to say it would not weaken the wheels. Is this just a myth? Can anyone help me out?

Also, does anyone know how much weight powder coating might add to a Z06 wheel?

 

I am interested in hearing more too.

 

You're kidding, right?

 

I have mine powdercoated and have put the car through many of the events that you described with no visible signs of distress.

 

YES it will make you crash backwards because the wheels will disintegrate due to the powder coating process!!! lol sorry I had to.

 

I use CCW wheels on my autocross car and know John at CCW
very well. In his shop he has a set of wheels with the centers torn
out. He told me one of the ALMS guys powdercoated the wheels a
couple of times to get the wheel color to match his car

Anyway, on race day the centers ripped out. John send the wheels
out to be tested and said the parts tested at almost "dead soft alumnium".

I think I would pass on powdercoating.

Russ

 

Some powder coating uses temperatures as high as 475 degrees. I think this is too high for aluminum, and could anneal (soften) it, although it usually takes 550-650 degrees to anneal aluminum (but powder coater's ovens could be off or have hot spots). I would NOT risk it.

Appearently there are powder coatings that cure at under 300 degrees, these are recommended for wheels. Look at this article:

Found your article most enlightening. A metallurgist friend told me a few years ago that things like aluminum wheel spindles should not be powder coated. He explained that aluminum billet material (6061-T6 ?) changed crystal structure at a critical temperature around 410 degrees F (as I recall). The thrust was that the heating step would adversely affect the strength of the material. Non-structural components would be OK, but not something that "holds the spokes on". The metallurgist is correct. Products like wheel billets, scuba tanks, etc. can be powder coated, but only with powders which cure below peak metal temperature of 300 degrees F. The magic temperature is about 275F. The crystalline realignment at 400 degrees F causes the previous ductile aluminum to become brittle. Imagine the catastrophe when an 80 cu. ft. scuba tank explodes under 3000 psi pressure after an unauthorized powder coat (this actually happened). To my knowledge, all Aluminum wheels and other strength-critical aluminum components are powder coated with these cooler curing powders.

 

 

Thanks for the helpful info.

 

I have had many wheels powder coated, mainly motorcycles with no problems. I would just use a good powder coater. All the bike wheels were alumnium and see speeds way into triple digits. A lot of motorcyle wheels come powder coated from the factory.

 

powdercoatng is a process where a positively charged powder is applied via spray or fluidized bed to a negatively grounded part, opposites attract hence the excellent coverage. The powdered part is then heated to cure the powder. In some cases especially when doing cast iron the powder is sprayed onto a preheated part then cured. curing temperatures differ with different powders, epoxy, polyester, vinyl, etc. all have different cure rates based on a certain amount of time at a certain temperature. Ask the powdercoater to use the lowest temp. longest time cure cycle. If they are experienced and knowledgable they will be have this info on hand or get it from the powder manufacturer. just $.02 from a 20+ year powdercoater/plater.

 

To be honest, I have used powder coating on a lot of diff car, motorcycle and industrial applications and not real impressed with it. imo if you want a durable LONG lasting finish use poly or acrylic urethane paint with a catalyst hardner. It wont fade or become brittle. I know there are people who swear by it, but there are also people who swear at it. JMO

 

To chime in with some anecdotal evidence, I have personally seen powdercoated wheels break under stress where normally the same wheels can handle it (Forged BBS wheels that come on Subaru STIs being used in SCCA rally).

 

The problem with powder coating aluminum it has to be baked on about 20-30 degrees under where the aluminum will begin to start to anneal and soften up. So you need some really good and accurate temp control in the process. I would be sure whom ever does it, knows what they are doing, and has the right kind of equipment to monitor the heat (baking). But if it's controlled, there shouldn't be any problem. And powder coat is way more durable than any acrylic or urethane paint. Don't think so, try bead blasting that stuff off.

 

Dude I've been rallying since 1995 and no matter what wheels you have soon or later that potwhole, tree root, rock, whatever is going to break a wheel really easy. You rally?

 

Had my wheels baking soda blasted they can out fine, no damage or alum. removed just old finish.

 

The difference was these busted new the first time out, not the normal "sooner or later" wear and tear. Also, from speaking with the guy, it wasn't even that hard of an impact, just hit the right rear on the foot high dirt berm.

 

Per Chip Huff at CCW "Sorry we don't do powdercoat. Aluminum doesn't like the heat"

 

I called a local powder coating company and asked him about it. He said the low temp coatings are really limited to about 4 or 5 colors. He then said to match or get the color I wanted, he could reduce the temp to around 300 and leave it in the oven for a longer period of time. He said he has had no problems with any of the wheels he has done so far but didnt know if any were used in competition or not. Also a question comes to mind if heat is so bad for the alum what will happen to all those who have had their wheel widened? Will they break at the weld? Is the problem with heat over a long period over a certain temp or just getting up to a certain temp? I saw an article about annealing aluminum to help form it for a car project and all they did was hit it with a torch to anneal it but it of course is a lot thinner than a wheel. I hate to go thru the hassle of painting my wheels if its safe to powder coat them at a lower temp. I doubt I will be competeing but I wont rule out bounceing off a curb by accident. Tough to decide. His price of $300 for 4 wheels didnt seem so far out of line when materials to paint them are going to run at least half that maybe more.

 

To further explain an above post, the aluminum in these wheels is peak age hardened (what T-6 means in the previous post). This works by precipitating Copper out of solid solution and hardening and strengthening the Al. What the heating during the powder coating does is provide the driving force for the precipitates to grow beyond the optimum size diminishing the effects of the age hardening. I'm not sure how long they are held at this temp, but any time above 300 F is going to cause a weakening of the material.