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Thread: Powder-coating aluminum wheels?

  1. #1
    Join Date
    Nov 2006
    Location
    Anchorage, Alaska
    Posts
    801

    Default Powder-coating aluminum wheels?

    This question may have been discussed in the distant past, but I'm getting serious now.

    When i built my Caterham in 2007-10, I had the Caterham wheels custom-painted in an Audi silver-gray color by Wheel Enhancement, the specialist Porsche-wheel outfit in California.

    Wheel Enhancement told me that they don't powder-coat aluminum wheels because "the heat needed to cure the powder-coat will soften the wheels."

    The wheels looked great -- for a time.

    Well, the custom painting hasn't worked well overall -- the paint has easily chipped off of all sharp corners on the wheels, like the bolt-hole edges, etc.

    In addition, my spare tire/wheel fell off at speed, and needs to be re-finised.....duh...

    What is the latest and best thinking on powder-coating aluminum wheels?
    Alaskossie

  2. #2
    Join Date
    Aug 2009
    Location
    Littleton, Colorado
    Posts
    820

    Default

    I powder-coated a set of forged wheels on my old Elise and never experienced any problems.

    I am thinking about getting Cerakote applied to the wheels on my Storker. The stuff is very durable and extremely lightweight. https://www.cerakoteguncoatings.com
    - Brunton Storker, LS3, Chassis 159

    Check out my build:
    http://www471.pair.com/stalkerv/gall...2_itemId=30849

  3. #3
    Join Date
    Nov 2006
    Location
    Anchorage, Alaska
    Posts
    801

    Default

    Mike,

    Actually, i wasn't thinking of the weight of powder-coating....

    But I know,"the ounces make the pounds."

    I'm looking at powder-coating as offering range of colors, I hope close to the painted Audi color that I have now.

    Thanks for the advice!
    Alaskossie

  4. #4
    Join Date
    Apr 2007
    Location
    Bozeman MT
    Posts
    486

    Default

    I don't know enough about the properties of aluminum to speak intelligently but it seems odd that the heat of powder coating would affect the hardness of the wheels. Powder coat typically needs to run at 425 - 450 to get the epoxy in the powder to do its thing and it seems surprising that this would be hot enough to change the molecular structure of the alloy.

    Does anyone here know enough about aluminum to say for sure?

    dave

  5. #5
    Join Date
    Dec 2008
    Location
    Port Angeles, WA
    Posts
    243

    Default

    Annealing heat treatable aluminum alloys is generally done between 650-825 degrees. Some alloys can be partially annealed in the 400-500 range. It's really alloy dependent, and we rarely know what alloy wheels are made of--hence the rule of thumb to never powder coat aluminum wheels.

  6. #6
    Join Date
    Feb 2017
    Posts
    36

    Default

    Aluminum wheels are powder coated all the time. Powder coating is done at around 400 degrees. Some areas need to be masked off, seat area for lug nuts, mating surface wheel to disk.
    Last edited by waltermitty; 02-25-2017 at 10:01 AM.

  7. #7
    Join Date
    Oct 2007
    Location
    Salt Lake City
    Posts
    294

    Default

    I once had the big idea to teflon coat the inside of a cup for a siphon-feed paint gun. Oh, how it was going to make my life easier! I must be a genius!

    Well. I had a friend do it (He worked at a military contractor and he'd sometimes do gun parts etc too). I filled the cup with primer and rotated the clamp lever. It bent the posts 20 degrees with no effort. Apparently that aluminum that the cup was made from completely changed properties when baked at 550 degrees. It had become as soft as lead. So much for that grand scheme. I had to withdraw my application to MENSA in shame.

  8. #8
    Join Date
    Jan 2006
    Location
    Seattle-ish
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    1,116

    Default

    Based on what I've read, this is one of those "it depends" scenarios. Lots of people powder coat their wheels with no issues, but I have occasionally heard of wheels that have subsequently broken. I even know of one wheel vendor whose warranty explicitly denies coverage to problems arising from powder coating. The crux of the issue seems to be the age hardening process. Depending on the alloy, that is done at a temps near or below those used for powder coating, over a multi-hour period. If the cumulative aging time for the wheel with powder coating is over the accepted range, then the tensile strength will be lower. If it is still within the target time range, then there is no negative affect. For example, 356-T6, which is often used for cast wheels, is aged at 305F-315F for 2-5 hours. In this example, if the original age hardening was done close to the 5 hour mark, powder coating could tip it over the edge for the application. If it was only done for 2 hours, then it would be fine.

    To be safe, I'd contact the wheel manufacturer and ask their opinion.

    -John
    Westfield SEiW
    2.0L Duratec
    Throttle Steer

  9. #9
    Join Date
    Feb 2017
    Posts
    36

    Default

    Another option on forged aluminum wheels is hard anodizing. It only comes in one color, a dull grey. but the finish is very durable and light.

  10. #10
    Join Date
    Feb 2012
    Location
    Roswell GA
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    892

    Default

    "It depends" is a valid answer. I have designed dip brazed aluminum assemblies using 6061 alloy. The process involves dipping the fixture parts in a molten salt bath at 1100F then the assembly is removed and air cooled. After inspection the assembly is heat treated at 350F for a number of hours (4 to 6). This hardens the alloy to the original T6 condition.
    Since someone doing power coating may not be an expert on aluminum alloy identification, not doing structural/safety related items is a CYA thing.
    Life happens while you're making other plans
    1995 Caterham Crossflow RHD
    1990 Miata
    2013 Mini (Her's)

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