Cyanide free cadmium plating
I'm a chemistry lecturer at a university in South Africa. A local manufacturer of automotive parts, asked me for information on cyanide-free cadmium plating. Unfortunately all the libraries here have only books dating from the 1940's and earlier when cyanide plating was the only workable option.
Are there commercial processes for cyanide-free cadmium plating? Where can I obtain more info?Johann L Fischer
Rand Afrikaans University - Johnnesburg, Gauteng, South Africa
Yes, there are commercially viable cyanide-free cadmium plating processes based on cadmium sulphate or cadmium fluoborate. If you go to any of the major manufacturers of plating solutions I think they will be able to offer you a process.
My personal opinion is that switching to cyanide-free cadmium plating is sometimes a mistake because it lulls people into a totally unwarranted sense of security. Yes, cyanide is an acute poison. But cadmium is a cumulative poison.
As common as cyanide cadmium plating is, I've never seen the air filled with cadmium oxide dust in a cyanide shop; and as rare as acid cadmium is, I've already seens clouds of cadmium oxide in cyanide-free shops a couple of times. For the safety-conscious person, this one is a tough call.
Ted Mooney, P.E.
Pine Beach, New Jersey
I would suggest that the automotive company follow in the footsteps of most of the world's auto makers. That is to eliminate Cadmium completely. The automakers have gone to either zinc plating (with better passivates), or to Zinc alloys such as : Zinc/Nickel; Zinc/Iron; Zinc/Cobalt; or even Tin/Zinc.
In accordance with the Brussels protocol, no automobile in the European Community will be able to be recycled if there is Cadmium plating on it. Further, they also state that Hexavalent chromates will not be permissible passivates for the sacrificial plated coatings. Non Chromate passivates, or trivalent passivates are currently being worked on worldwide.
I have run both cyanide cad and sulfate cad. The output of each was quite similar. The cyanide cad was much easier to keep in balance. The three component additives that we used are no longer made, not enough demand. It was the very old 3M system.
Current additive use a chemical that I forget the name of, but it smells like dead fish and is a regulated material.
The future is in the alloy zinc. If they are going to drop cyanide, they might as well make the switch to alloy zinc.James Watts
- Navarre, Florida
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