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Jet Black Passivation turns brown

May 8, 2008

We are currently passivating metal parts jet black using a standard process namely, first we zinc plate in a standard zinc cyanide solution.Then we rinse and activate in a propriety solution followed by a further rinse and then submersed into the jet black propriety solution.This is then rinsed and dried with warm air.Our jet black passivation process starts off jet black, however within a week it turns brown and eventually it is dark olive green. This is seen by the differance in colour indoor (black) versus outdoor (brown). Please advise how we can get the process to stay black in colour when viewed outdoors.

Nick

Nick Steyn
Quality Manager - South Africa

May 8, 2008

Hi, Nick. The source of the black color is probably a light-sensitive silver. This problem is very common. Consider switching to zinc-iron plating because it can be reliably blackened without silver in the passivation solution.

Regards,

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

Are those parts rejected? How can we convince customer that these parts are not rejected?

Avinash Vidhate
- Nasik, Maharashtra, INDIA
October 22, 2008

October 27, 2008

Hi, Avinash. I don't know the terms of your purchase order or the function of the parts you are plating. But I understand your customer's problem with parts that are supposed to be Jet Black but are actually first brown and then olive green. I suspect that the parts are rejects.

Regards,

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

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