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How to zinc plate and powder coat on same part





2003

Q. We are currently processing assemblies using cold rolled sheet material. These require plating per ASTM B633 [affil. link] -85 TYPE IIFe/Zn 8. After this process one side of the details is masked for powder coat painting, cure temperature for the powder coat is 400 degrees. With this temperature the zinc plating gets cloudy and has a white tint. This is not acceptable to our customer.What can we do to avoid this situation.

RICK CARTER
- ROUND ROCK, Texas



2003

A. Perhaps I'm missing something, but I would have thought it would be more practical to do the powder coating before the plating.

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Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey



"Zinc Plating"
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2003

A. Sounds to me like you are dehydrating the chromate in your baking of the powder paint. The gold color is imparted in a post plating operation called chromating. The chromates are what really provide your corrosion resistance by forming a hydrous (spelling?) chromium barrier on the zinc. Heating above a certain temperature will dehydrate the coating and the chromate will no longer protect the parts. Visually it appears as you have described.

Bill Grayson
- Santa Cruz, California



2003

Q. WHAT WILL HAPPEN TO THE PAINT WHEN IT GOES THRU THE ZINC PLATING PROCESS? WILL IT DEGRADE THE FINISH AND DURABILITY OF THE POWDER PAINT? THANK YOU

RICK CARTER [returning]
- ROUND ROCK, TEXAS USA



2003

A. That depends on a number of factors, and may require some development work. But what I can tell you is that people do mass produce products like this by doing the powder coating first and then the plating. Powder coating can be very resistant to all plating chemicals; I've seen this successfully done even when the process sequence involved both cyanide plating and chrome plating. Good luck.

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Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


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