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Black spots in cyanide copper plating

July 1, 2010

We're into cyanide copper plating, we are facing a problem as mentioned below:-
After plating MS screws in cyanide copper plating by barrel method, after some time on the threaded portion we are finding some black dots on the plated surface. what could be the reason

warm regards,
Thyagaraj

V Thyagaraj V Thyagaraj
plating shop employee - Bangalore, Karnataka, INDIA

July 6, 2010

Hi, V. When cyanide-based plating exhibits dark spots or dark areas after some time, it is usually "cyanide bleedout". The way to solve it is better rinsing: possibly alternating hold and cold rinses, possibly an ultrasonic generator in a rinse tank, possibly a neutralizing agent like sodium bicarbonate, possibly a final D.I. rinse. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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