I agree with allot of what both partys say to an extent. I posted my heat treating process for 6061 forged centers and wheels to achive a T-6 condition.

In order to achieve a T-6 condition for 6061 aluminum the part must go through a cycle of anneal, solution, and precipitation heat treatments. Each process has a time and temp starting at about 775F for 2-3 hours, then solution of 970F for ** (memnon trade secret) and then precipitation treatment to get to T-6 at **F (memnon trade secret). The whole process takes 6-10 hours. Achieving T-6 should give the aluminum a 42000 lbs ultimate, 35000 lbs of yield strength with a 8% to 10% elongation MINIMUM.

Powder coating has a series of washes then powder application. After the powder application, the full amount of heat required to melt the powder is only 350F-450F for 15 to 30 minutes max. This time and temp is based on generic powders and doesn't take into account special color or compounds. The amount of time in a powder oven should not change the temper of a forged center or wheel.

I've made plenty of 18" track wheels with 15" brakes and ones that have cracked are due to thin spoke cross sections not coating. The brakes on a track cars can see 700 to 800 F. The fact that the wheels can handle these temps means a 300 degree temp for coating should not affect the overall strength of the wheel. The track is an unforgiving ***** and the coating that holds up the best is powder.

YseanY is correct anodizing has color consistancy issues and when I have to make 3 sets of wheels for each car and one gets trashed, trying to get the same color anodized again just doesn't happen.

IMHO, powder coating is the best and most durable coating for the money and really shouldn't have any adverse effects on the performance or strength of the wheel.

 

300 degrees YES.
400 degrees NO.

 

 

There are no necessary "washes" the part needs to go through before coating except a possible denatured alcohol rinse just to make sure the part is clean.

 

I'm still unconvinced that the annealing process that takes temps almost twice what the curing process needs for 6-10 hours that taking the wheel to 400 for only 10 minutes reduces the strength as much as stated.

 

From the Alcoa handbook:

Melting point of common forged alloys: Degrees Fahrenheit

1100 1190-1215 F
2024 935-1180
3003 1190-1210
4032 990-1060
5005 1170-1210
5056 1055-1180
6061 1100-1205
6063 1140-1210
7075 890-1175

 

Here's an interesting article I found about powder coating wheels:

http://www.parkerionics.com/new-tech...uminum-wheels/

 

Just to verify a couple of things.

YseanY says.

Since Tech1 Mike did not object to this statement is it correct to infer that anodizing is indeed safe for wheels?

And do the concerns of powder coating forged wheels also extent to other production methods such as flow forming?

Thanks!

 

While anodizing may be safer, it doesn't mean powder coating is not safe. One big difference is the small selection of usable colors, 2 for anodizing and around 8000 in powder.
The only issue I have with the Parker-Ionics story is when the guy mentions "Exceeding 350°F for an extended amount of time can begin the aging process and make the aluminum too hard."
I contend that 10 minutes @ 400° is not "an extended amount of time" to start the aging process.
For 10 years I've challenged anyone to show me one documented case that proves the wheel failed due to proper powder coating process.

My research has shown that aluminum alloy may be weakened by 2-5% if heated too high, too long. I also believe wheels are not made to 100% of critical use factor, but probably more like 125-150% to relieve the company of liability. So losing 2-5% off 150% still leaves the wheel at 142.5-148%, more than enough to not worry.

Bottom line, again, is that the powder coating process is not harmful to the wheel IF IT IS APPLIED AND CURED PROPERLY.

I am currently working on coating $2K ea. carbon fiber wheels.

Anodizing is an electrical process to place a layer of oxidation on the wheel.

 

Anodizing is safe for forged wheels. No high temps are used.
There are few colors available and many anodized finishes are vulnerable to fade and discoloration from UV (sunlight).
Powdercoating is safe when performed by experts who understand the heat treating properties and how to test for material hardness.