Summary for zinc cyanide replacement Discussion
Using zinc cyanide as sodium cyanide replacement is not recommended in this cadmium plating question. F.J. Visagie of Cape Town asked whether abundant zinc cyanide could substitute for missing sodium cyanide while making additions to a cadmium solution, since procurement was slow. The only answer in the thread came from an unnamed responder who said, "Sorry but I can't imagine that working," and did not offer a technical workaround. The reply leaves the idea unsupported and suggests that the two chemicals should not be assumed interchangeable in this context. No one in the thread provided a tested formulation change, so the practical takeaway is to treat the substitution as doubtful and seek proper cadmium-plating chemistry rather than improvising with zinc cyanide.
Q. Good Morning Fellow Platers.
We run a plating shop and are busy doing additions to our solutions, we realized that we don’t have sodium cyanide for our cadmium solution. As procurement takes ages, we were wondering if we could substitute sodium cyanide with zinc cyanide as we have an abundance of the stuff. Any advice is welcome.
F.J. Visagie
– Cape Town, South Africa
June 25, 2024
A. Hi F.J.,
Sorry but I can’t imagine that working. Still, your inquiry is on line if anyone can offer encouragement
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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A. Hello F.J.
When you add sodium cyanide you are adding ‘free cyanide’.
it will attach to the cadmium metal allowing it to remain soluble in the hydroxide matrix. additionally there is an excess of cyanide in order to allow cadmium to dissolve into solution from the anodes.
Zinc cyanide acts like the cadmium and it too has cyanide ligands attached to it in this solution, so it does not add to the overall ‘free cyanide’ content. The sodium is just present as a carrier ion and does not co-ordinate strongly with the cyanide. that is why it is added to the solution. Also, the zinc may also plate along with the cadmium onto your components changing the characteristics of the coating.
Mark Lees
– A dull grey rock in the Irish Sea