I think I know the answer to my question, but I'd like some insight from people who maybe have been here before.

I have a set of BBS LM wheels for my C5 that I am super excited to get onto the car. The only problem is that the centers are currently navy blue, which is the same color as my car, but definitely doesn't do it for me as far as color is concerned.

I went to my local bodyshop that has done some work for me in the past to get an estimate to have the wheel centers painted and they elected to pass on the job, saying that they felt they wouldn't be able to get the spoke areas painted cleanly to their standards. They recommended to just have them powdercoated. I had gotten a recommendation for a reasonably local shop that specializes in powder coating and has a good reputation.

I swung through there with one of the wheels and they took a look and gave me a relatively reasonable price. They had felt that the wheels were actually previously powder-coated blue based upon the way the wheels looked. The person at the shop said that the wheels would have to be chemically stripped and then sandblasted, coated silver and then cleared.

My concern is that these wheels are forged. I'm already a bit stuck as the wheels have been PC'd once which who knows how good or bad they were done. Judging by the condition of the blue, I'm confident that the wheels have been driven on for some time, so I'm not necessarily worried that they are damaged in their current state.

So I guess where I'm at now is do I risk the second powder coating for the centers. My heart says not to, to have them chemically stripped (either by a company, or by myself with a whole load of aircraft stripper) and then refinish them myself with a few cans of Wurth silver metallic (OEM BBS Paint).

Conversely, if anyone from MA has a hookup for a way to refinish the faces for less than $500 not using powder-coating, that would be fantastic.

 

Pics?

 

They are almost a perfect match for the OEM navy blue, I'd just much prefer the OEM silver.

 

Wish I could help you concerning refinishing the wheels, but I have no experience with that. But I will say I kind of like the centers painted like that.

 

I like them more than I should, admittedly...but the condition of the blue is meh @ best, and the silver is such a classic look.

 

I would try painting them myself, without stripping them. It will cost next to nothing and you have nothing to lose. You can always go the expensive route if you don't like them.
I have painted wheels before with great results.

 

Try plastic-dip. I've had great results with it.

 

I'm going to have to agree with AlienC4 at least in the short term. There's a few silver/metallic colors to choose from and if done properly they'll look pretty good, plus it'll just be the centers. Roll on dipped wheels until you can find a reputable place that can do what you're looking for and by then you should have done extra funds by then.

 

As long as the chemical stripper doesn't eat at the metal, there shouldn't be any issue with having them stripped in that fashion. Just make sure the shop knows what metal they are working with.

You could always hit the blue with an ultra fine grit wet sand and see if that cleans it up.
Or use a scotch brite pad to scuff the blue (for better adhesion) and respray them in the color you want.

 

Dude, you should disassemble the centers, and have them powder coated, HANDS DOWN. I would not even consider a standard HVLP paint job on wheels, it always fails early. Nice thing about powder coat, chemically stable

 

For less than the 500 bucks to have them powder coated, you could buy a good compressor, spray gun, paint and all the materials needed to paint and clear coat them.

Get some satisfaction of doing something yourself. You can get a professional finish that will last a long time.

 

I don't mind the idea of derping them if they were one-piece wheels and I wanted to test fit, but if I'm breaking the wheels down and reassembling them, I only want to do it once. I've yet to see Plastidip with enough gloss for what I'd want, long term.

The blue is chipping and was laid on thick. I've thought about doing a scuff and shoot, but where it's chipping I don't want to set myself up for an uneven surface.

I've done tons of reading on heat cycling wheels, I don't want to go the PC route again. Honestly, it's bothering me that they were PC'd once. I know that failure is rare, but why take the chance if you don't have to. If there was a local place that specialized in low temp work, that would be one thing, but I don't want them just thrown in a 450°F blast furnace either. I know there's huge debates in both directions, but after my reading, that's my feeling on the matter.

 

I don't understand your concern? Powdecoaters strip powder off aluminum daily. All they use is paint stripper.

Im currently re-doing my wheels, I broke them down myself and my powdecoaters stripping my centers and re-powdering satin black and even doing my inner barrels for $320

 

Wait.
You're cornered about heat cycling the wheels from a 450 degree oven for 20minutes ?

It's amazing our blocks and heads are still good then huh

 

Let me take you to school for a minute, but first a little background. I have degrees in both metallurgical, and polymer sciences; which are hard science fields dealing in the physical properties, and practical application of metals, and plastics. I also work in aerospace, and regularly am involved in stress analysis of aluminum parts, in compromised situations (basicly if someone screws up an important part, a study has to be done to determine the best thing to do structurally for the plane as a fix).

First of all, the heat treating method of annealing (the mechanical softening of metals through heat) for aluminum is 572-710 degrees in fahrenheit (higher for forged alloys, like your wheels) which is the temperature required for the molecular structure of aluminun to open up, and relax natural stresses in a given piece. 450 degrees will NOT hurt your wheels, and no one uses a blast furnace for this sort of thing, the particulate output of an open flame would cause surface contamination in the coating, which happens to be plastic (like all paint). Rather, a big autoclave, or electrically heated paint booth are the typical methods found in practice of such a procedure.

Secondly, if you have your centers media blasted with lets say, plastic media, it will have both the benefits of creating excellent tooth for paint to stick to, but also shot peen the surface for the piece, which creates a residual stress layer covering the entire part, making it mechanically less likely for cracks to start, or propagate, and also releases interior stress, while releasing surface tensile stress.

At the end of the day, your not only getting a surface with superior cohesive properties, and strengthed alloy through cold working, but your also coating them in a material that (because it uses electricity to bond the particals, NOT solvents) is not only chemically resistant, but also much more resistant to scratching, and has a much higher hardness then standard HVLP paint applications.

So really, powder coating is THE ONLY METHOD that makes sense....scientifically

 

PLUS if this was really an issue, then at least 75% of all wheels, including factory mags, would be suspect to failure because of powdercoating, which makes exactly-0 sense considering it's wide use as a wheel coating by effectively every major automotive manufacturer. THIS is the science behind it, everything else is speculation by people that like to think they know what they are talking about. There is a lot of mouthpiece out there, don't be discouraged by uneducated paranoia.

 

Wow ErikwithAK01 - great information.

I had talked to the manufacturer of my forged wheels and was told that re-coating was fine as long as whoever was doing it knew what he was doing as temps above 450 would change the structural properties of the metal. Your info is consistent with that.

I have a question for you. I never got an opportunity to refinish them as the anodized wheels cracked in the middle of the spokes.

I cut out the cracked sections and took some cross section pics on both sides. Is there anything in the attached pics that would suggest anything to you?




I have also heard that the anodizing process may also weaken the structure. Is this true?

I am just trying to gain an understanding of what happened to satisfy my curiousity.

Original poster - apologies if I am hijacking. If there is an issue with that I can PM Erik, just let me know.

 

MikeyMcfly...nice wheels - I don't have any suggestions other than what about stripping them then do a brush finish followed by a clear coat? Probably more than your budget, but theybwould look sick, especially if you have a dark colour.

Good luck with whatever you decide to do.

 

First off, in reality, fatigue strength is proportional to starting crack size, and if anodizing can prevent scratches (which eventually originate into fatigue cracks) it would only improve fatigue strength. Secondly anodizing prevents contact with the elements (much like paint does) with Aluminium which prevents stress corrosion cracking, once again improving fatigue strength. Furthermore, the layer of aluminium oxide is so small that it can't seriously be extrapolated to reduce cross sectional area, which would translate into reduced strength.

So to answer your question, NO, anodizing does NOT reduce the structural integrity of a part on the scale of a car wheel.

Now, in all honesty, a small amount of surface is altered with an acid, like sulfuric, or chromic acid, which does technically reduce the strength of a part by reducing cross sectional area...but depending on the material used for anodizing, that can be as little as 0.0001 of an inch, to 0.010 for the more aggressive processing. Your usual processing usually only uses the prior, and 1-ten thousandth of an inch, is NOT going to effect a car wheel.

Without being able to physically handle the material, it is hard to say what caused it. Typically, a part thought to be strong, and defect free, will break in this manner when it's base materials engineered limits are exceeded...too much nitrous hehe! However, it only takes a small surface defect to eat away at structural metals that go under heat, and/or stress cycles regularly. Bellow is a pic of a lab experiment where they scratched the surface of an aluminum rod, then applied stresses to it until it completely failed. You can clearly see how a small surface scratch can propegate until the part fails entirely.

 

I learn new awesome things everyday! Thank you for the science lesson sir!