Brighteners used in Silver Plating (Potassium Cyanide bath)

A. In the cyanide-nitrate bath, 1.5 mg/liter/hour. I'm sure you could hook this up to an ampere hour meter pump.

A. Please visit the Chemicals Directory for chemical suppliers. Proprietary additives are provided by chemical companies, and then you don't have to waste time making them yourself. It rarely is worth the effort to make your own brighteners.

A. We use ammonium thiosulphate solution. It depends on how bright you want your parts and what else you want the brightener to do. You may need a proprietary brightener if you need more than just a little brightness.

A. The best brightener and additives for silver cyanide bath is selenious acid and potassium tartrate antimony. 0.2-2/lit selenium and 0.05-1.5/lit antimony. Good luck

? Hi Dom. Do you have Hull cell test equipment and have you tried any experiments with it yet?

A. Dear Mr Sideri,

To analyse for Carbonate content: pipette [pipettes on eBay or Amazon] accurately a 10ml sample of plating solution into a 600 ml squat form beaker [beakers on eBay or Amazon]. Add 300 mls of de-ionised water and heat on a hot-plate with a boiling rod in the beaker.*DO NOT BOIL** Add 10% Barium Chloride solution until no more precipitate forms in the beaker then filter through a Whatman number 40 filter paper. Wash the filter paper and beaker thoroughly with hot de-ionised water until the final washings no longer turn pH indicator paper blue. Transfer the filter paper back to the original beaker, pulp up and add 200 ml of de-ionised water and a few drops of methyl orange [on eBay or Amazon] indicator solution. Titrate with 1.0N Hydrochloric Acid while stirring the pulped filter paper with the boiling rod. End-point is; Orange to Red.

Calculation:

Titre mls x 5.3 = g/l Sodium Carbonate
Titre mls x 6.91 = g/l Potassium Carbonate

A. Hi John.

There is no such compound as silver potassium. You might be thinking of potassium silver cyanide. But there are dangers both of generating poison gasses and making explosive silver fulminates if you are mixing things and inexperienced in silver chemistry. Plus, practical silver plating baths will need addition agents which are usually proprietary. For 1 liter of silver plating solution, I'd strongly urge readers to buy it rather than try to make it. Good luck.

Regards,

A. Hello, The difference would be in the grain structure of the deposit. For example, antimony is a common brightener and would make the deposit harder than just a matte silver plate. For switching parts it makes sense that the deposit has to be harder for better wear resistance.

A. Antimony and Selenium brighteners interfere with radio frequency, carbon disulfide brighteners do not.

A. Hello, I did some research on the subject and could not find any remedies for a high concentration of antimony. I do have a few questions however. Are you using pure silver anodes, and not silver/antimony alloy? What current density do you normally employ? What is the temp of the bath? Are you adding the brightener according to a amp hr schedule, if so what is you addition rate? Are you adding your drag-out rinse back to the bath? You may have to resort to decantation of the bath, without the addition of the antimony brightener of course. The reason I'm asking the aforementioned questions is for preventative measures, to avoid excess brightener concentration that may occur in the future. Look forward to your answers.

A. Good day Ruben.

I would contact your brightener supplier.
As Mark has indicated, a decant would help, also with your carbonates if they are high.
High Ho Silver!

Regards,

? Hi Ridwaan. Your question is unclear to me. Are you asking that vendors of proprietary brighteners contact you with their offerings? Or are you conducting research into the formulations?

A. You could start with a literature search of the technical articles about silver brighteners. Scholar.google.com is very good for such stuff; and MFIS/Finishing Publications in U.K. offers CD-ROM and on-line access to their abstracts of the surface finishing literature.

Luck & Regards,

A. Ask your supplier and they will help you. In Sweden they use the same brightener for all silver by Atotech, Candor, MacDermid etc. The brightener contains selenium and its trade name is AgO56.
Regards,

A. Hi Senthil. If I'm guessing right, Majed suggested trying 0.2-2 mg/lit selenium but 0.05-1.5 g/lit antimony. After you confirm a workable value in a hull cell test, you can scale it up to your tank size. Good luck.

Regards,

A. Hi Mohit. I am not familiar with potassium iodide being used in potassium cyanide silver plating. How much is there and why (where can we find the suggestion for it)?

If your product is buffable (like flatware), thiosulphate should be fine. If not, please either consider a proprietary silver plating process, or ask a question about the many solutions proposed on this thread over the years. Good luck.

Regards,

A. Hi Mohit. Hopefully a reader who is familiar with using silver iodide will help. As I've said, I personally haven't ever heard of it, so I can't conjecture whether you have too much or too little, nor can I suggest what other brighteners are compatible with it. I personally agree with Tom Pullizzi about using proprietary silver bath where you will get operating instructions and help, plus the benefit of decades of experience.

Beyond that, this page reveals many years of experiences with various generic brighteners: Jeanne says "ammonium thiosulphate" is good for moderate brightness; Majed says "selenious acid and potassium tartrate antimony. 0.2-2/lit selenium and 0.05-1.5/lit antimony" (and I think he means 0.2-2/ mg per liter selenium but 0.05-1.5 grams/liter of antimony; Nigel suggests that lack of brightness may be excessive carbonates and tells us how to analyze for them; Goran tells us to NOT use silver iodide, but to use "15 gm silver nitrate, 30 gm sodium thiosulphate [on eBay or Amazon] , 100 gm ammonium chloride" instead. Mark tells us the antimony helps with hardness if that is important to you. Robert tells us you need to use carbon disulphide instead if your brass wire is used for radio frequency rather than decorative application. Good luck.

Regards,

A. Hello Maribel,
This would be a question best answered by your silver bath supplier. I know when I was working for a leading supplier, the silver brighteners could not be analyzed by titration, but that was some time ago. Responders on this site may shy away from giving you an exact method of removing the selenium from the bath, as it could affect your production schedule and cause you more headaches if things went south. I would rely on your supplier, as they know the chemistry you use the best.

A. Hi Maribel,
Unless you have an on site lab able to conduct inductively coupled plasma emission spectrometry with hydride generation it is best left to the chemistry's suppliers as stated by Marc. Here is a link to paper that delves into the selenium effects and analysis in KAgCN baths.

https://www.sciencedirect.com/science/article/pii/S0026057600834017

However what problems are you having with your tank and deposits? If the selenium is that high and can't be directly contributed to a single "bad" add it is likely been climbing with brightener adds trying to correct another issue. Most commonly K2C03 (potassium carbonate). if the additions of the primary brightener were made to fix high current area burning, dendritic deposits, or just an over all dull columnar grain structure it might be correctable without going directly after the high amount of selenium. If you find your carbonate levels higher than recommended reducing them with a good decant will have a much more dramatic effect on the finial deposit then reducing brighteners. The brighteners can be reduced in the decant as well. Carbonates in most KAgCn solutions are recommended to stay below 8 oz/gal but even up to about 15 oz/gal is still very functional with good agitation. Good luck.

 Thank you so much for your replies Mr. Mark Baker and Mr. Chance Dunstan!

We are aware of the procedure but I wanted to make sure if there was any other from years ago or a recent one.

I want to prevent any future issues by not adding a high amount of selenium-based brighteners.