Ted Mooney, P.E. RET
- Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Cyanide copper plating on zinc diecast
Q. Hi, my name is Afzan and I am from Pakistan. I do copper cyanide plating on zinc diecast. My cyanide plating is getting tiny pores -- it's result is the zinc starts dissolving in bright nickel and my parts are getting small black spots.
I do my cyanide plant carbon treatment but this action does not solve my problem. Please kindly help me. I am very grateful to you.
Afzan Khalil Ahmed- Lahore Punjab pakistan
October 12, 2024
A. Hi Afzan
Cyanide spot-out on zinc diecastings is a fairly common problem. Eliminating it requires at least four things:
• Decent diecastings. If the diecastings are porous and full of cold shuts it can be impossible to plate them short of vacuum impregnation.
• Proper mechanical pretreatment. If the diecastings are not properly de-flashed and de-burred you will have spongey areas that will hold the cyanide solution and it will slowly bleed out. But if the pretreatment is overdone, wearing all the way through the 'skin' you will expose the porous innards of the castings.
• Proper anode material. You need good quality oxygen-free high conductivity (OHFC) copper.
• Proper rinsing/neutralization of the cyanide. After a good initial rinse, a dip in very weak sulfuric acid is suggested. See Robert Probert's explanation.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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