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Composition and property data of clear chromate

To whom it may concern:

Where can I find information on the composition and property data of Clear Chromate?

I am also interested in any testing information on leaching for this substance.

A client is concerned about leeching of his clear chromate coated ice machine.

Paul Marshall
- Questline
2002

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Any of the chromate manufacturers (Plating chemical suppliers) can give you a MSDS. It will have some trivalent chromium, possibly some hexavalent chromium, nitric acid, maybe some complexed cyanide. Chromate process design is in a state of flux, and chromates have always varied anyway, such that I would not trust a generic approximation--it would have to be based on the brand actually used.

If this surface is in contact with potable water or ice I would think it a problem.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

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I was reading this question and I am also interested in the composition of Clear Chromate - as well as other Chromate passivations such as Yellow, Olive Drab, and Black Chromates.

I have posted a question on this website before and it received some excellent responses, but I still have not been able to locate a good and comprehensive source of info on the chemical composition of these coatings when they are in the final (dried) state as deposited on the substrate part/material. I am not concerned with what the recipe of the bath is.

I work for an OEM supplier and I do IMDS reporting. It's my job to document exactly how much (if any) HexChrome, Cadmium, Lead, and Mercury is in each and every one of our parts in effort to comply with the European Union's ELV directive.

I am aware and understand that the amounts and ingredients of these coatings DOES vary from supplier to supplier, but I mean how much can it REALLY vary? I just need a good source of info that would make my job a lot easier because a lot of our parts have coatings such as Zinc & Yellow Chromate (dichromate), or similar coatings. The problem I have is that our parts may be purchased from one of our suppliers, but it is often coated by one of their suppliers, and so trying to track down and get information from whoever it might be about the coating is worse than pulling teeth.

Is there not some sort of general reference source where I could obtain this kind of info about these coatings? I would just like to bypass the headache of contacting all these different suppliers to help me save time and provide consistent data in my reports. Please help.

John Warriner
- Lakeland, Florida, USA
2002

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I eagerly await an answer to your question, too, Mr. Warriner. But I don't have the confidence that you have that the differences are relatively minor. The fact that corrosion performance varies radically among instances of the same type of chromate, the fact that plating shop operators make adds when they feel of a mind, the fact that the concentrations of chromic acid in the same type of chromate vary by something like 4 to 1 between brands, the fact that some use accelerators of one type and others don't--all of this means to me that you may need to go by a maximum or a statistical average rather than a standard value with a small variance. I haven't personally ever tested the composition of the coating and I hope that you are right but I doubt it.

I think it's coming down to accepting that you can't use any hexavalent chromate at all when there are going to be very tight restrictions on the amount that can be in the product. I wish you well in your quest for data.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002