Metal Finishing Question - Non-cyanide based continuous wire plating
Was wondering if you could help me out with a plating question. Below is a question I have placed on the P2 Tech and National Metal Finishing Resource Center listserves. Was hoping that www.finishing.com might have a similar network to help get some feedback on my cyanide alternative question.
I look forward to seeing what turns up. Thanks in advance for your help.
NH Dept. of Environmental Services
Pollution Prevention Program
I am currently working with a fine gauge wire manufacturer under an innovative pilot program called CLEAN-P2 (Compliance Leadership through Environmental Assessment and Negotiation - Pollution Prevention). The intent of CLEAN-P2 is to offer a full compliance and P2 evaluation under an enforcement relief package. If we find compliance issues, we let the company know what they need to do (without fear of enforcement actions) and ask that they utilize P2 to get back into compliance (where appropriate and *doable*).
The company conducts a number of processes, but the main one of concern (to the EPCRA inspectors, the RCRA inspectors, and to me as the P2 contact) is a continuous, silver on copper, electrosilver wire plating operation that utilizes potassium cyanide solution. Once plated, the wire is further processed in-house (wire drawing, twisting, flattening, etc..)
The question -- Has anyone worked with, or have knowledge of, alternative, non-cyanide based continuous wire plating systems. The benefits of eliminating cyanide from the facility are hopefully clear.
Vincent R. Perelli
New Hampshire Department of Environmental Services
Pollution Prevention Program
6 Hazen Drive
Concord, NH 03301-6509
A thought from E.F. Schumacher in 1973 - "We must begin to see the possibility of evolving a new life style, with new methods of production and new patterns of consumption; a life-style designed for permanence"
Frankly, cyanide, a naturally occurring poison, does not concern me very much from an environmental perspective as long as reasonable destruction technology is applied to the waste; but from the safety perspective it is a very frightening process, and should be eliminated when possible. The reason for the use of cyanide in this case, which you may already appreciate, is that silver is more noble than copper and will immersion deposit unless highly complexed. It is difficult to complex the silver without cyanide. Further, silver plated out of simple salts is light sensitive.
While there are some cyanide-free bright silver plating solutions available, Alan Blair writes in the Metal Finishing Guidebook: "As yet, no production-proven, noncyanide alternative has been found, although systems based on thiosulfate and succinimide appear to offer some promise." Considering your need for silver plating that is sufficiently ductile for drawing and flattening, the prospect is even more discouraging. But I would suggest that you contact the suppliers who have been doing development in this area, starting with Technic in Providence, Rhode Island.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
I feel for you in your search to remove cyanide from your silver plating operation. I too do electroplating on wire (exclusively) and have yet to find anything that will work anywhere near as well. One of the problems of overcoming this obstacle is to not only come up with a non cyanide plating bath, but to create one that is efficient enough for high speed reel to reel electroplating of wire.
And so while I cannot offer any hope (I have personally given up the search for now,) I can don my saftey gear and salute you.
- Lansdale, Pennsylvania, USA
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