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Black deposits in ID of silver plated mouthpieces

Q. Hello everyone, I hope you can help me with my problem, we have a silver solution of 500 lt, 16 g/l of silver cyanide, 120 g/l of potassium cyanide, the brighteners are within the range, we make silver coatings on musical instruments of brass.

61563-1c

61563-1a 61563-1b

When we do the silver plating we have deposits in internal areas of a dark black tone that comes off easily and the brass is exposed very clean matte,; does anyone know what could be happening? We made a hull cell and the tests come out fine; this It only happens with large pieces, with small pieces everything is fine.

HECTOR DIAZ
- MEXICO/ ESTADO DE MEXICO
July 28, 2023

A. Hi Hector.
The plating only goes where the current flows, and in direct proportion to it. But the current tries to take the path of least resistance, and there is no current flowing to the interior of the long mouthpieces.

I don't think you will be able to plate them except with an auxiliary anode (a wire running through the center of the mouthpiece, and connected to the anode).
Luck & Regards,

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

Q. Hello Ted Mooney, we already did that test, we placed an auxiliary stainless steel anode that passes in the middle of the hood, making sure that it does not collide with the piece and is connected to the tub that we use as anode by means of a cable with an alligator, we obtained the same result.

61563-2

HECTOR DIAZ [returning]
- CIUDAD DE MEXICO/ ESTADO DE MEXICO
July 30, 2023

A. Hello Hector, Sorry for the delay answering your question. I think plating the ID of the longer mouthpieces you may have to position them in a more horizontal way to force more solution though the piece. If the parts remain stationary during plating in a vertical like position you will have problems. There has to be solution movement through the mouthpiece with use of a auxiliary anode. Do you have solution movement from a filter system or cathode bar agitation? If you don't replenish the silver ions within the inner diameter you will have problems with the longer pieces.

Mark L BAKER
- Cazenovia, New York USA
August 10, 2023

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