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I had style 44's powder coated last April.

1: I waxed them monthly and cleaned them with neutral pH soap exclusively.

2: After only 3 months and only 1000 miles of summer driving (no snow not once, no salt on the road) they developed what looks like "spider web" cracks all over the finish.

3: In places they also developed yellow "tiger spots" from what looks like brake dust eating into the finish. It can't be cleaned even by professional detailer chemicals.

It's really hard for the camera to pickup the "spider web" cracks, but in sunlight they are very visible:


There is only one shop that does it, there are no other options, they have no competition and I guess no drive to improve. Ironically I paid extra money for the clear coat top coat as "extra protection".

Is anyone experienced with powder coating? Any guess what they could've done bad? Cheap material? Bad preparation? What can I tell them so they don't just use the standard excuse "you must've washed them with something aggressive".

I won't pay for powder coating every driving season, that would be absurd. Yearly sandblasting and oven heat are surely not very good for the aluminum anyway.
 

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I had my style 68s powder coated this summer. After 3 months one of the the wheels had a spot flake off. They just took the wheel and redid it. No questions asked.

Sounds like you have a clearcoat failure. Just take it in. You don't need to tell them you did anything to the wheel. Just point out the failure and ask them politely to make right.

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This seems like a prep/process issue to me. I don't work in a powder coating facility but occasionally I deal with suppliers that powder coat parts for the company I work at. On our prints for our aluminum wheels and other large parts we include a note that requires sand blasting and pre-heating prior to coating. The pre-heating helps with adhesion and reduces the time for the part to come up to final temp in the finishing oven. Baking for too long or at too high of a temp can make the finish brittle or cause amber colored burns. The spider cracking makes me think your wheels may have been over baked.

It's also possible they used clear powder that wasn't appropriate for coating wheels. You should ask for the spec sheet on the powder they used and check the temp rating. Even under normal driving wheels get hot... If the clear wasn't designed for high temps then it could lead to the failure you're seeing.

Here's a sample spec that we use on some of our parts (zinc rich primer, top coat, no clear) so I'm not sure how helpful it will be.

Also, this is some good reading on TGIC curing agents vs HAA. For clear coat I think TGIC is preferred since it's less likely to yellow if over baked.

https://www.powdercoatedtough.com/News/ID/650/Technology-Interchange-Polyester-Powder-Coatings-TGIC-vs-HAA

 
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