Summary for cyanide copper plating Discussion
Cyanide copper plating on zinc diecast is the focus of this thread, where Afzan reports tiny pores in the copper layer that let the zinc dissolve during bright nickel plating, leaving small black spots. The reply from Ted Mooney suggests a practical troubleshooting path: if the black spots appear after stripping and replating, check the cyanide bath chemistry first; if the spots remain in the same location after replate, the issue is likely not the plating bath but something wrong with the part material itself. The advice implies that the defect may be tied to the diecast substrate or a persistent surface flaw rather than a one-time plating error. The discussion is brief and does not offer a detailed root-cause analysis, but it points to bath control and part inspection as the key next steps.
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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Ifzan.
AFTER CYANIDE PLATE BLACK DOT/SPOT ON PART, BLACK SPOT PART STRIP COPPER AND REPLATE AGAIN, SAME SPOT IF YOU CAN SEE REPLATE PART CHECK CYANIDE BATH CHEMISTRY
IF NOT BLACK SPOT SOMETHING WRONG ON PART MATERIAL.
Popatbhai B. Patel
electroplating consultant – Roseville, Michigan