Observational standard for trivalent black zinc

We are supplying a new part to a large contract manufacturer that gets Trivalent Black Zinc. Our supplier for the black zinc is approved by and plates for several automobile manufacturers including Toyota and Honda for black zinc.

Problem is that the contract manufacturer does not like the black zinc on these parts that we have supplied for them. We are thinking that our customer may be expecting too much from a cosmetic standpoint from this black zinc.

Are there any observational standards for black zinc out there?

Hi, James. Interesting situation because the typical response of "zinc is a functional, not decorative, finish" begs the question: "if looks aren't a valid issue, then why is there even such a thing as black zinc?"

I know of no universal industry standards for aesthetic appearance, but that doesn't mean that everything is acceptable; it means that sample boards of acceptable and unacceptable parts must be negotiated and then maintained. Good luck, and 2nd opinions welcome.

Regards,

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