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Powder coat masking problem with aluminum

I have some 6061 T6 aluminum parts which have a drilled hole and the inside of this hole must be electrically conductive.

I had these parts powder coated (by a partner in Taiwan) and the drawing shows the hole masked from powder coating.

When I received the parts, the hole looks like it has been masked but there appears to be a baked on clear coating on the inside of the hole. The rest of the powder coating is black so what ever is inside the hole is visually different. I am fairly certain the coating on the inside is not Aluminum oxidation and what ever it is makes a very lousy conductor. I have to either re-drill the hole or figure out what in the process caused it. Any ideas?

Wally Hall
product designer - Denver, Colorado, USA
October 13, 2009

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Hi, Wally. My guess is that it is a masking material that the powder coater forgot to remove, or they misunderstood you and applied this clear coat thinking it would be okay. Maybe you should ship the parts back to Taiwan and let them deal with it since they know what they did.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 14, 2009

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First of two simultaneous responses --

If you buy parts from the lowest bidder, you normally get a corresponding quality. Throw in a language barrier and you get the fun that you now have.

James Watts
- Navarre, Florida
October 14, 2009

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Second of two simultaneous responses --

It sounds like the coating might be clear anodize.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
October 14, 2009

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Your answers better than mine.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
October 15, 2009