Run_Away
Run_Away GRM+ Memberand Dork
8/6/21 1:47 p.m.

Hey y'all

 

What are GRMs thoughts on powder coating forged wheels?

Safe?

100% chance of exploding?

Should be fine if you only street drive, but will crack if tracked?

 

Seems a topic the internet feels strongly about and I haven't seen it discussed here.

Have my heart set on some wheels, bought a pair for the rear and made them fit. Now having a hard time finding a pair for the front in the specs I need with the same finish. Would you do it? Or stick with paint only if refinishing.

stuart in mn
stuart in mn MegaDork
8/6/21 2:41 p.m.

From a powder coating company website: https://www.prismaticpowders.com/learn/26/can-aluminum-wheels-be-powder-coated  I tend to agree with them, as long as the temperature of their oven is not too high and they don't leave the wheels in there too long it should be okay.  I think there are also some powder coatings that can be cured at lower temperatures, which may be worth looking into.

For what it's worth, I had the wheels on my BMW powder coated ~10 years ago and I haven't burst into flame yet.  smiley

A question that is often asked is, "Can an aluminum wheel be powder coated?". The simple answer is Yes. Countless wheels have been powder coated and driven on without issue.

However, whether or not an aluminum wheel should be powder coated has been the topic of some internet debate. No doubt the subject is full of rumor and conjecture, sparked by a relative few wheel failures subsequent to having been powder coated. Here we will attempt to make your decision a little easier by bringing some facts to the conversation.

While some manufacturers will void the warranty of a wheel if they are powder coated, countless OEM and aftermarket wheel manufacturers already choose powder coating for their preferred finish. The list of which includes some very high end and prestigious names (unfortunately for legal purposes; we can not name-names).

The debate seems to stem from the possibility of wheel failure after going through the powder coating process, and whether or not the heat required to cure the powder coating is enough to damage or weaken the structural integrity of the wheel. Usually the debate is focused directly on aluminum, not steel because aluminum anneals or "softens" at a much lower temperature.

  • Aluminum anneals at around 650°F
  • Steel anneals at a much higher temperature (1300°F)

Standard powder coatings cure at temperatures that range from 350°F-400°F. The time spent at these temps (Part Metal Temp) averages about 10-20 minutes. This is far below the 650°F needed for the aluminum to soften.

In fact, there are aspects of part preparation such as the blasting process, which may be more of a hazard to aluminum than the curing process. Depending on what kind of media is used, the blasting process may result in a degradation of the substrate.

OEM manufacturers must consider these aspects, and issue such warnings against modifying their products (including the finish) to protect themselves from liability and litigation. 

You too must consider the facts and possible risks to decide for yourself whether powder coating wheels is something you want done, but always consult a reputable powder coating shop when having your work done.

pirate
pirate Dork
8/6/21 10:45 p.m.

If it truly is a forged wheel rather then a cast wheel it will be stronger because of the flowing microstructure. A lot of forged wheel use 6061 aluminum alloy. These alloys artificially ( heat treat) age/harden at temperatures starting around 350F to 500F but in cycles of 12 to 24 hours. Solution heat treatment or annealing doesn't occur until 990 F followed by water quench. Powder coating at temps of 400 F for less then an hour shouldn't affect the microstructure at all. As long as you use a reputable powder coating who pays attention to curing times and temps you should be fine.

My only issue  with powder coating of wheels, suspension components and chassis/frames is it makes crack detection difficult or impossible. Probably not a factor on a street car but may be an issue with a race car. Cracks are probably not and issue with wheels unless damaged by impact or bending at which point you know you have a problem.

frenchyd
frenchyd UltimaDork
8/6/21 11:14 p.m.

In reply to stuart in mn :

 I don't think it can be a problem.  Do you realize how hot the brakes on a race car get?  Disk brakes start glowing red at what? 1200 degrees and yellow about 1400?  The disk is less than a couple of inches away and the caliper closer than that.   I've watched racers glow their brakes in 24 hour races. 
 Forged wheels are easily capable of that treatment. 

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
8/8/21 8:09 a.m.

In reply to pirate :

I have seen a few cracked spokes on wheels, NONE of them were bent.  This would be a fatigue failure, not a single impact hit failure.

Have seen rims dented enough to cause a crack that leaked, but that isn't the kind of crack that is a safety hazard.

Run_Away
Run_Away GRM+ Memberand Dork
8/8/21 1:17 p.m.

Wheels are Volk CE28s. The factory finish is anodized with a painted lip, so they scratch easily and aren't the most resilient to corrosion.

It's for an auto-x car that gets street driven, so I'm not bouncing it off track curbing but I'm not hard parking either.

Searching around and you find stuff like this suggesting you'll be weakening the wheel going back to 400 deg for an hour to bake the finish

 

But then of course brakes generate a ton of heat. TBF, wheels are expected to be consumables on vehicles used in those conditions.

It seems most powder coating related sources say yes, and all wheel companies say no.  Lots of variables based on the original wheels strength, how the original coating is removed, how the new coating is applied, etc. Add that to the unknown history of a used wheel and I don't think there's a definitive yes or no.

Run_Away
Run_Away GRM+ Memberand Dork
8/8/21 4:46 p.m.

https://digitalcommons.lmu.edu/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1009&context=mech_fac
 

Really good stuff in there. Basically says powder coating is safe, only makes a difference in repeated cycles at high temps.

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
8/8/21 5:27 p.m.

I would think that if that much brake heat got absorbed into the wheel, it would cook the grease out of the bearings before it got the wheel hot enough to anneal it.

chandler
chandler UltimaDork
8/8/21 5:30 p.m.

Powder coater will always say yes, wheel companies will always say no because it's not in their control. I've done it and run those wheels in various styles of motoring and not had an issue. My Wedsport RS5 broke in the original pink (it was red but faded horribly) color though so there's that.

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