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Black spots after copper coating

"Electroplating and Electroless plating of Copper and Its Alloys"
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"Copper & Copper Alloy Plating"
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Q. Dear Sir,
I am getting black spots after copper coating of carburising treated low carbon parts. Kindly guide me for correction

Jay Sona
Metlab, Supplies Quality, Heat Treatment, Projects - Rajkot
September 22, 2025

A. Hi Jay,

Frequently, 'cyanide bleedout' can be a cause of spots and discolorations.

I and the readers are happy to help, but it is rarely the case that a given problem has a single possible cause. To expect that would be like phoning a doctor that you have a fever and expecting him to tell you exactly what is causing it.

Please send a picture of these spots, and tell us a bit more about the processing, and hopefully we can be more definitive.

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.

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