Is Powder Coating bad for rims?Shea Bethell
The short answer is yes, and its even illegal in certain countries including Germany! Even just using heat to bend damaged rims back into shape is not allowed.
There are many Powder Coating establishments, including ‘rim repair professionals’ that powder coat and then bake rims at temperatures between 150C and 200C for around 15-20 minutes. What if we told you that baking aluminium alloy wheels at 150C to 200C will permanently weaken them? The aluminium used in rims is annealed when received new from the mill, which in laymen terms means they heat up the metal and let it cool in a controlled environment in order to create strong grain structures in the alloy.
The baking process after powder coating will bring the rims to a high enough temperature to begin changing this annealing. The TUV, or Technischer Überwachungsverein in Germany certifies all items and processes for vehicle components. Without TUV certification, an item cannot be used on any Germany roads.
During refinishing or repair TUV completely forbids any alloy rim from being heated past 90c (194F) for any period of time, and for a maximum of 40 min for temperatures under 90C.
“Eine max. Einwirktemperatur/ -zeit von 90°C/ 40 min. darf bei Lackierarbeiten nicht überschritten
werden. Pulverbeschichtungen mit höheren Temperaturen und Einwirkzeiten sind nicht zulässig. Auf
Grund des Wärmeeintrages und/ oder der Benetzung mit Lacken, wird empfohlen, vorhandene Ventile nach den Lackierarbeiten zu ersetzen.”
Now what about how the majority of repair shops that fix damaged rims? They apply heat. Why? Because it softens it and allows the metal to bend back without the risk of cracking or splitting.
What does TUV think about this?
“The repair of a damaged rim or disc by heating, by welding, by addition or removal of material is absolutely forbidden”
The reason for completely not allowing welding or heating to fix bends or cracks is also due to annealing. By heating one part of the rim, not only are you changing the crystalline structure of the metal, but you are also making it inconsistent in spots.
The only permissible form of repair for bends is cold pressing, and even then is regulated depending on severity.
The next time you need rims repaired, stick with painting and insist on bends being cold pressed; your safety and those of others depend on it.