Metal finishing Q&As since 1989

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Can Customer Prohibit Cyanide in Zinc Plating?

April 25, 2008

We are an electroplating job shop and recently we received a specification by one of our clients with the following restriction:

"The use of CYANIDE in the chemical composition of the electrolytic bath is
prohibited."
"The use of HEXAVALENT CHROMIUM in the passivated layers is prohibited"

We understand that according to RoHS and ELV regulations we have to avoid HEX Chrome and other metals and products, but we have never heard of a restriction to use CYANIDE.

We understand the Hazards associated with handling Cyanides and dissposing of waste streams containing cyanides, but not using Cyanides to zinc plate, where the final finish (and part) has no cyanide in it, it seems unreasonable.
Cyanide is used mainly as a grain refiner in Cyanide Zinc Baths and no one will be exposed to it by touching or handling zinc plated parts, as compared to the handling of Hex Chrome passivates, where this is a risk factor.

What opinions or experiences does anyone have regarding the restriction of zinc plating with a Cyanide based chemistry? We can't change to non cyanide baths at the moment, and we are aware of the advantages/disadvantages of this.
Any and all comments will be appreciated.

Sergio Hernandez
Finishing shop - Guadalajara, Mexico

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Hi, Sergio. I hate to be glib by saying this is a very interesting situation, because we understand that it is a serious matter for you, not an intellectual exercise.

I believe that it is within your customer's rights to impose such a requirement even if it doesn't make sense to you. We are in an age of activism with respect to environmental matters, and I would expect more of the same -- usually achieving nothing useful, but occasionally actually advancing a good cause, and sometimes doing more harm than good. God save us from good intentions :-)

In the case of zinc plating it is relatively easy, in concept at least, to convert to acid zinc or alkaline non-cyanide, and I think you should plan for it even though you say you can't do it today -- because a meme on the loose spreads like wildfire; so if you somehow talk the customer out of this requirement, it's quite possible that another will impose it tomorrow.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 28, 2008