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-----Black spots after copper coating
by N. Kanani
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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
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
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