inactiveuser92616

if anything I would guess that the cracks, if a result of powder coating, were caused by differential expansion rates between the aluminum wheel and the powder coat.

Eyal 951

just casue one guy, who worked at a PC shop says its okay (its his, or was his job to, almost any pc shop would say so) doesn't mean its true. (doesn't mean its false either, you guys are just taking his word as omniscient) There must be a reason that this information is widespread, and pretty well know. True or not, I won't be PC'ing my wheels.

OriginalSterm

Instead, your professional opinion is that it weakens the material? He stated some chemistry/materials science, what is your personal experience to the contrary?

Zero10

I am going to powdercoat my phone dials. They are my winter rims anyways (i.e. are fitted with winter tires), so they don't see a lot of stress.
However, my sewer lids which house my track tires will remain faded and un-powder coated just to be safe

User 41221

FWIW, I just got off the phone with a representative from Fikse, and while I was talking to him, I mentioned powdercoating... he immediately said "no way!". He didn't get into it, but he obviously didn't like the idea. He said anodizing the wheels is a much better way to go. The folks at Fikse ought to know what they are talking about (altho he wasn't able to give me a great answer as far as how to keep my #$%^&!!! FM10's clean!).

I don't know a lot about the subject, but I would have thought PC would be no big deal, and would have thought anodizing would be potentially worse on the wheel. I have no knowledge to offer this discussion, unfortunately.

Regards,

Manning

So by your logic stereotypes exist for a reason

Manning

Continuing with the line of thinking in this thread, what kind of temps are seen with anodizing. From what little I know, anodizing is chemically reproducing a type of hardened surface that could theoretically exist naturally, no? Then you throw in some dye to make it pretty.

inactiveuser92616

yes, anodizing (for aluminum) is the artificial creation of the hard aluminum oxide layer that naturally forms. Basically it is a chemically/electrically accelerated corrosion, creating a thicker layer of the hard aluminum oxide than would form naturally. The dye is just brought in as part of the process.

DanD

So while were on the subject of Rims. How about chrome plating?

Or better yet, how do you remove chrome plating?

inactiveuser92616

chrome plating does damage the wheel from what I understand, atleast it damages steels. The process causes the phenomenon known as hydrogen imbrittlement.

bleucamaro

Ok, here's the verdict. . . sort of. This topic really peaked my interest, so I did a bit of research. To begin with the basics, many (most) OEM cast aluminum wheels (typical alloy is A356) are powder coated, including BBS wheels. See excerpt below.
That seems to cover cast wheels, except for the lack of disclosure of both the alloy and powder coat cure schedule used, so I dug a bit deeper and conferred with a couple other ME's at work, who had the general consensus that it would not harm the wheels, but these guys are mechanical and aerospace engineers, not metallurgy experts. I continued my search for a definite answer, and took it to a higher authority, the interweb. I started a thread on eng-tips.com to see where I stood, as seen here à http://www.eng-tips.com/viewthread.cfm?qid=151053 . The opinions of the engineers there varies, some saying its safe, some saying that more information and testing should be performed, but to use caution.

The consensus was the condition causing fracture would be from over-aging, where the grain structure passes beyond an optimum state. The extent of this would depend on cure temp and time, more-so depending on temp. Also, the extent of the reduced strength from over-aging using a 400°F for 1hr cure schedule would need to be tested.

One of my coworkers, a stress analyst, suggested that someone post pictures of where the cracking is occurring, saying that if its on the outside part of the spokes, its more likely to be caused by side loads, and if its towards the center, its more likely caused during braking. He added that the extreme brake temperatures can cause heat transfer from the rotor to the wheel. Again, to quantify this testing should be done.

It is still my opinion that powder coating is a safe process for cast aluminum wheels,
but I would like to see some hard data before powder coating forged wheels on an aggressive cure schedule. I still plan on powder coating my D-90’s.

If you question or are uncomfortable with your local powder coater’s practices, then find a reputable one to deal with.

Patrat, the difference in thermal expansion rates can be negated because powder coating can stretch and flex so much.

In the case of crack detection, powder coating’s flexibility is a major downfall because it becomes possible for the metal under the coating to crack without the coating cracking.

Dan D, the method we used at the powder coating shop to remove chrome was to blast it off using aluminum oxide or garnet. It takes forever and is not a fun job.

The hydrogen-embrittlement issue and anodizing issue would be a good question for Steve, KuHL951, but my experience with anodizing is that it provides good protection to the part, but tends to fade and chalk up when exposed to UV.

Eyal, I am not currently affiliated with the powder coating industry, and when I was I would not push someone to coat something that shouldn’t be coated. It’s not for everyone, or everything, but is a great finishing method.

I fear that the problems people are having with their 20 year old track wheels is that there is micro cracking happening under the surface, and under the paint, or the wheels are reaching the end of their fatigue life. It would still be hidden if the wheels are re-painted. It is my opinion that if someone is racing on wheels this old, they should be die-penetrate inspected.

Anyway, I’m tired of typing, so I hope this provided some resolution.

Cliff’s Notes: OEM’s powder coat their wheels, and some engineers say its safe, some say it causes over-aging. I’d powder coat a cast wheel, but am leery about coating forged wheels.

Supachink

I have a set of mila miga knockoffs that were chromed and the chrome is beginning to flake off, would powder coating these wheels be a bad idea? What are the knockoffs made of? Can you strip / beat blast the chrome and pc it to stop the corrosion underneath the chrome