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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Pulse plating caused silver plating problems
Q. We were using Normal D.C. Rectifier previously, we were replenishing our bath by adding:
1) silver salt (containing cyanide)
2) carrier additive and
3) brightener.
Everything was going good, but after replacing our rectifier with a pulse rectifier the thickness of contacts is reduced by a great extent. I will be pleased if somebody advises how to maintain the same thickness.
Thanks,
chemist - Baroda, Gujarat, India
2003
A. The recommended "windows" for setting pulse and periodic reverse are generally proprietary. It will vary with your bath chemistry also. If the power supply manufacturer cannot provide you with the information that you need, you bought it from the wrong manufacturer. I think that there has been a book published in the last 5 or so years that includes a number of possible starting points. A search of the net might find it for you. AESF (www.nasf.org) is one possibility. This site has a listing of many books and a link to amazon.com
James Watts- Navarre, Florida
2003
A. One of the more common problems with cyanide baths is a loss of cyanide resulting is reduced efficiency. If your cyanide levels are correct, then check you have calculated the rectifier conditions correctly. It used to be a widely held belief that pulse plating increased the efficiency of electroplating - it DOES NOT, - this is controlled by Faraday's Laws. Some years ago, some pulse plating systems were falsely sold on the basis of improved efficiencies. Make sure you have calculated the correct number of coulombs you need. If you are using a reverse pulse, remember to take that into account when you are calculating the process parameters - the reverse pulse will strip silver off the workpiece. Also make sure you have the correct pulse cycle conditions, as localised electrolyte depletion will reduce plating efficiency. Pulse plating can also adversely affect the way additives behave, so you may have to watch for that as well.
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003
A. Hi,
Dynatronix have a web site with frequently asked questions and answers.
Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2003
A. You want to get the same outcome as before, so why don't you get back to your tried and true practice (old rectifier)? You said it was doing just as good.
Guillermo MarrufoMonterrey, NL, Mexico
2003
2003
Q. Hi,
We are a Finish plating shop. One of our services is to silver plate RF filter bodies. Normally we use inert anodes to have silver about 6µm into deep holes. Now we have a bit too difficult filter body and I am planning to use pulse plating to get desired thickness.
The base material is diecast aluminium and electroless nickel 10µm on it.
My question:
Does anyone have detailed information how to start or where could I have a copy of article (from AESF): Title: "Optimization of Throwing Power in Pulse Reversal Plating from a Silver Cyanide Solution" Authors: P. Leisner, P.T. Tang & G. Bech-Nielsen Reference: AESF SUR/FIN'94, Indianapolis (1994)
Thank you and best regards,
- Kellokoski, Tuusula, Finland
A. Hi, Petri. The article will probably be available from www.namf.org, although you may need to buy the proceedings of the whole session rather than just the single paper. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003
Brown discoloration spot in non-cyanide silver plating
September 23, 2014Hi, I have a problem with plating discoloration. I am using non-cyanide plating. Discoloration shape is always circle inside and area, a small round circle -- usually appears with a negative height from the surface, and light brown color.
Can you suggest how to resolve this issue?
Thank you.
own - cavite, philippines
A. Hello Ado,
From what you are saying the spotted areas appear rather consistently on the part. If the remainder of the part is plating well, I would suspect this would be a cleaning issue or particulate matter. Before going into the silver bath do a water break test to make sure the cleaning process is in order. Also you want to make sure the solution is particulate free (suspended solids). Non Cyanide Silver salts don't dissolve as well as Silver Cyanide Salts, so you want to make sure the salts completely dissolve before you begin plating. Check the Quality of your filtration, change filters often. Hope this helps!
Process Engineer - Phoenix, Arizona USA
October 8, 2014
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