Asked for Clear zinc plating but got Blue

A. Kaith,
It would be a better idea to show a sample of the color you require to your vendor.This has been always an argumentary situation to differentiate between clear passivation and blue passivation. In some occasion blue is considered clear and vise versa.
So I think first you yourself have a clear idea about the color you want and work towards getting it with the help of your vendor. But pl. keep a the color sample in front of the vendor.
Regards

A. Thanks, T.K. I felt pretty much the same, but wanted to hear someone else before I replied.

I have seen some chromates that are very clear and I have seen some that are quite uncontestably blue (and I'm not talking about blue dye). And many chromates are in-between, and I am probably as guilty as anyone else of referring to them as "clear" or "blue" interchangeably.

Your advice that, if color is important then samples must be maintained, sounds good to me.

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

A. I guess I'll never convince anyone but myself, but...there is no such thing as "clear", ie, colorless chromate. All chromates are colored to one degree or another. If there is no color, there is no chromate. Period.

First of two simultaneous responses --

A. Keith,

The blue or clear color of zinc-plated with tri-chromate passivation components are most likely depending on the concentration, temperature, pH of chromate solution, and dipping time in chromate solution. It is blue color with shorter dipping time (10-20 sec). It is less blue or clear (as your color requirement) with longer dipping time, 30 to 60 sec, or longer. Blue color will give you thinner chromate film. Less blue or clear color will give you thicker chromate film.

I would accept both colors as color appearance variation for zinc-plated with tri-chromate passivation components, however, I prefer the less blue or clear color because thicker chromate film will provide slightly better corrosion protection.

Regards,

Second of two simultaneous responses --

A. Many of the Automotive specs that I have read, specify clear and blue separately and have different performance expectations from them. They are not to be confused with each other.

Clear normally indicates a Hexavalent Yellow or Hexavalent blue that is bleached colorless sans any shade of yellow or blue; clear could also be achieved by various topcoat dips over the chromate, not necessarily by bleaching.

If the parts are blue instead of clear but meet the specified corrosion resistance criteria, then apart from the color there should be no issue in using them.

If not then there is a step missing in the process and you need to replate, since clear normally outperforms blue in any corrosion test.

warm regards,