I am not claiming anything. We don't recommend powder coating our forged wheels. I have made it CRYSTAL CLEAR why.
You will have a VERY hard time finding a Forged Wheel company who will recommend this process. Good luck.

As to your motives during your first six posts on this forum, I will let the members decide.

 

So what we can gain from this is basically you have made a recommendation based solely on your opinion and not technical data.

 

No, what we gain from this is that you know absolutely nothing about the risks of powder coating forged wheels. It is obvious to me that you don't even know what a Brinell hardness test is.
Any degradation of tensile strength is unacceptable to us. We KNOW as a FACT that heating our wheels to 400+ degrees fahrenheit causes the annealing (softening) process to begin. Since there are hundreds and maybe thousands of powder coating companies out there and since we have no idea what they will do to our wheels, or what skills and quality systems they have, we don't recommend the process.

 

Back you case up with numbers. I never said that it wouldn't start the softening process. I am only asking you to provide the numbers of how much it softens it. What is unacceptable to you does not mean that it isn't acceptable to 99% of the rest of the world.
Can you answer any of the following questions with your extensive knowledge in the field of metallurgy:
#1 How much will taking a wheel to 400f for 10 minutes decrease its tensile strength from the 50000psi?
#2 Can you show me any documented case where the wheel failure was directly attributed to the coating process?
#3 What is the safe range for tensile strength of a race wheel?

I am a professional custom powder coater and your statements prove to me that you know little if anything about my business and have probably done less research into coating than I have into metallurgy and the cause and effect of coating aluminum and magnesium.
All you have offered is an opinion you can't back up with true hard fact numbers. My challenge is still there.
I went through this same BS when people say you shouldn't sandblast and coat coil springs because the heat generated from blasting will weaken them. I did extensive test of spring rates on stock race springs before, after blasting, after coating, after over heating and found that in every test the springs still rated within the factory specs.

 

1. Our metallurgists tell us that 300 degrees is the maximum safe temperature for our alloy and for no more than 20 minutes.
2. I have two sets of wheels that failed in service due to overheating during the powder coat curing process. Their Brinell hardness was almost 20% lower than normal. I do not know the duration or temperatures involved. But THAT is exactly the point.
3. The safe tensile strength for any wheel is a function of the engineering, vehicle weight, front/rear weight bias, overload margin, and several other factors. There is no "fixed number".

I have no further comment on this subject.

 

So your opinion is related only to "your alloy"
While there are many cast race wheels out there that are in the 18000psi strength as you have indicated I find it hard to believe that your alloy of 50000psi will fail when it is at 40000psi.

Generally it is safe to coat any wheel if done properly.
Now let the members decide on what they want to do. I personally am not trying to generate any business from members here which is why I haven't included any plug for my business.
Common sense says to educate yourself on dealing with any business. But to just say coating wheels is bad is doing everyone a disservice.

 

Your comments are DANGEROUS and misleading.
The alloy we use is 6061/T6. We believe there is no safe powder coat cure exposure at 400 degrees fahrenheit for this alloy.
Cast wheels are normally made from an alloy called A356 which has totally different properties than 6061. The tensile strength of A356 varies widely, depending on the specific alloy and heat treat (if any) used.
HOWEVER, Reducing the tensile strength of a forged alloy by 20% (50,000 to 40,000) psi, would lead to CATASTROPHIC wheel failure in most cases.
This is because the load carrying capacity of the wheel would be reduced to the same degree.
You may know a lot about powder coating but you fall way short when it comes to forging, wheel engineering and the properties of forged alloys.
We stand by our position.
(Now you all know why.)

 

I thought you were through.

 

Hmm.... I'm gonna go out on a limb here (and not respond to any negative comments you might throw at me) and say that your overall tone and aggression would lead me to never work with you ever... on anything.

An informed discussion between two professionals (which Mike was trying to have) is what we, as a community, would prefer. You are clearly protecting your business by jumping into this thread, and forum board, and antagonizing someone who clearly, knows a lot more about wheels than yourself.

The question asked by the OP (Original Poster) was "should be worried about,ie reduced strength,". Now I have NO DOUBT that you know a tremendous amount of knowledge on the processes of powder coating.... unfortunately the process has NOTHING to do with the scientific facts about the degradation of metals exposed to high heat temperatures.

That's like saying someone that has been detailing cars for 20 years knows scientific info about how the properties of wax affect the molecular structure of clear coat and paint...... Yeah, don't freaking think so! You may know that in those 20 years, nothing has happened to anything you've worked on... but you're challenging scientific information with EGO.

Now I'm not saying that Mike is 100% right (because honestly I have no idea), but your willingness to dismiss anything, just because you don't think he's right is just ignorant. ....look up the definition, that's not an insult, you are basically the exact definition of it right now, or at least in how you've portrait yourself here on this forum.

ALSO... "I personally am not trying to generate any business from members here which is why I haven't included any plug for my business."

That fact that you haven't stated WHO you are or WHERE you work does nothing for you.... for all we know you could be some 18yo kid who just started a powder coating gig in your garage. I would MUCH rather know who you are. Man up and tell us who you are/where you work, so we can see how legit you really are.

 

I was merely trying to get him to back his opinion up with data to prove his point. He has still not done that. The answer to the OP is "No you shouldn't be worried about the reduced strength". While my process has NOTHING to do with the scientific facts about the degradation of metals exposed to high heat temperatures. I was at least smart enough to protect my customers by educating myself on the subject by spending hours discussing the facts behind my process and their effect on the metals with soeof the top metallurgists in the country. It just rubs me the wrong way when someone comes into a venue bad mouthing a process that he has little if any knowledge of. I am well respected in the industry and run a successful business.
www.creativecandy.org

 

I didn't bad mouth the process. I simply stated that we, among MANY other forged wheel companies, do not recommend 400 degree cure temps for our wheels. PERIOD.
IMHO you spent a lot of energy trying to bully me into agreeing with you. I don't. And I have conveyed a plethora of scientific facts to support the general forged wheel industry position on this subject.
You, on the other hand, after "spending many hours with some of the top metallurgists in the country" do NOT have a clue what a Brinell hardness test
is and actually advocate a reduction in tensile strength by up to 20%. DANGER DANGER DANGER!!!!!!!
You are clearly ignorant, uninformed and totally disingenuous.

 

While I may not have experiance with Brinell testing that is one of the reason I seek education from those who do. The ones I have spoken with in regards to coating aluminum and magnesium did not tell me the numbers were as extreme as your 20% and they said the process we use is not a concern for failure in and of itself. It wasn't until almost 2 pages of our discussion that you actually presented us with a number like I had asked for all along. I never tried to bully you into agreeing with me, I only asked that you present your opnion with numbers. I still have difficulty in believing that a wheel manufactured to 40000psi would fail at 30000psi after heating to 400f. And so it makes even less sense to me that a wheel manufactured to 50k would fail at 40k under the same conditions. So I still don't agree with your position and we should just agree to disagree. You posted one number supporting your position (50k reduced by 20%) so I would look up the definition of "plethora".

 

I have found this thread to be quite useful despite how it seems like the discussion may have gotten a little out of hand. I have been going back and forth on how to "paint" my forged wheels and I was settle on anodizing as that eliminates any risk altering the strength of the wheel and it is quite durable. But it seems like anodizing has a disadvantage when it comes to color matching as I want to match the Porsche White Gold Metallic. So my next options are wet painting (which can match the closest if not 100% but the downfall is durability) and powdercoat (which is very durable and colors can get very close, but there is the issue of heating the wheels).

It seems like the biggest issue is finding the right people to do the powdercoating. After searching around, I believe the annealing process a problem with my forged centers. However, from what I've gathered, as long as the curing temperature is within 250-300(?) degrees and the wheels are gradually brought up to this temperature, it shouldn't weaken the wheels. I think Mike's (and other forged wheel companies) warning is that we do not know if a powdercoater is 100% honest about the process and his curing temperature (not attacking the industry but this applies to any industry where people would take shortcuts). In addition, whether the powdercoater has the facility and equipment to closely monitor and control the temperature of the curing as aluminum absorbs a lot of heat and if you have the oven set at 300 degrees, the wheels may actually be at 350-400 degrees (threw out random figures as example).

So if I'm not mistaken, if you can find a powdercoater who understands forged aluminums and has the equipment to closely controll the temperature, then powdercoating should be relatively safe.

 

Sean, I have accomplished what I set out to do, let the masses know that hearing from both sides and coming up with an educated decision that fits your specific needs. In my oven I have the temp controlled by a PID. I also have hanging thermometers in the oven and at differant levels to check variables in temps top to bottom. I check the parts themselves with a IR temp gun to monitor temps during the cure process. If the three differant methods of checking temps are agreeing with each other there is no way for the temps in the oven to exceed by 50F that which it is set at. With the exception of radiant heat being transered from the heating element itself if the part is too close to it. I have metal heat shields over the elements to avoid this issue. As I mentioned before there are RAL color powders that cure at 325 instead of the standard 400f powders and this temp can be lowered by 5% or so for a longer cure duration to achieve a full cure with more peace of mind. Color selection is more limited with these powders but there is still a large selection to hoose from. I have a RAL color chart with 186 colors on it compared to the over 7500 colors I have available in standard colors. Any color can be blended though so there is an unlimited selection of colors and textures available to match any situation.

 

We use 300 degrees F as a maximum because we know it to be 100% safe. The problem arises when the parts of the wheel heat at different rates. If you examine a typical wheel spoke, it is almost never uniform in shape. It is thicker and wider near the bolt holes and thinner and narrower as it approaches the rim. When a powder coater says 400 degrees for 10 minutes, what does that really mean? What part of the wheel is heated to what temperature and for how long? How can you possibly measure this data? You can't.
What you can do is check the hardness of the alloy after heating it. This hardness is measured on the Brinell scale and is the GOLD standard for this technology.
Top quality powder coat facilities use computerized Brinell hardness testers and test each wheel BEFORE and AFTER curing. They use SPC (statistical process controls) and maintain detailed records on every part.
In our experience, 300 degrees has shown to eliminate any chance of over-aging or annealing the part. As the temperatures increase and the DURATION increases, the risk of alloy degradation also increases.
If you soften the alloy due to annealing, all of its characteristics change in a non-linear way. Tensile strength is reduced but elasticity and yield strength are also negatively affected. The wheel's load carrying capacity will be reduced, the wheel will flex more under load and will prematurely fatigue.
Because forged alloys are so sensitive to heat treating, we recommend they only be handled by experts who have the knowledge, experience, equipment and quality systems necessary to prevent damage.
So, in the end, if your powder coater doesn't even know what a Brinell hardness test is, I seriously question their competency at refinishing forged wheels.
Now you know what questions to ask.