Letter 26076

Cyanide-free silver plating solutions [Scotland] 

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As a technologist with Rolls-Royce, I have been pursuing a cyanide free silver plating solution which can adhere to a Woods nickel strike and give adhesion equal to that of commercial cyanide based solutions. Is it commercially, and chemically , feasible to produce a silver chloride based cyanide-free plating solution utilizing Potassium Chloride as an electrolyte for "throwing power"? Copper Pyrophosphate and electroless nickel can not be used as strike solutions for adhesion for the components I am looking to plate.

Nigel D Gill, B.Sc. MIMF
Technologist - Glasgow, South Lanarkshire, Scotland

Hi

There is a bath in the USA from a proprietary maker that fits your bill.

Ask around for the name as this column won't permit names.

Regards

Asif Nurie Atlanta Global Limited New Delhi, India

 Ed. note: We do try to keep this section non-commercial, Mr. Nurie, because over-commercialism reduces interest and because it's not fair to the site's supporting advertisers to ask them to pay the cost of public promotion of competing products from non advertisers. But if you know who offers what Mr. Gill seeks, please tell him in private. Thanks.

There is more than one available. Technic's Cyless Silver was probably the first. I think that it still requires a cyanide silver strike for some applications. The Mfg can certainly tell you.

James Watts
- FL

I have tried using Technic's Cyless silver, unfortunately it requires a copper pyrophosphate strike which IS NOT allowed as a strike prior to silver plating on the components I have as they are exposed to temperatures exceeding 500 degrees Celsius and copper oxidizes above 350 degrees C. Also Electroless nickel cannot be used as it is deemed to brittle. Silver Chloride based solutions using KCl is more like what I am looking for to achieve coating thickness of 7.62-12.7 microns.

Nigel Gill
- Blantyre, South Lanarkshire, Scotland

One of the producers is EPI (East Berlin, WI, USA) too (E 50/50 bath or something similar). Good luck! and two recipes:40 gm AgCl 200 gm potassium ferrocyanide 20 gm K2CO3 stainless steel anodes,1-5A/dm2, 80 C recipe 2:15-90 silver pyrophosphate K4P2O7 100-350 gm ammonium carbonate 20-145 gm o,5-12 A/dm2, 18 C (recipes are from USSR literature)

Goran Budija
- Zagreb, Croatia

A silver fluoborate bath would be interesting. I don't know if one is possible, but I know that the chemical, "silver fluoborate" exists. At least, here's a data sheet on it. http://www.conncoll.edu/offices/envhealth/MSDS/chemistry/S/Silver-tetrafluoroborate.htm

You could probably make it by combining stoicheometric amounts of Silver Carbonate and Fluoboric Acid. You can make, as a precipitate, the Silver Carbonate with Silver Nitrate soln. and Sodium Carbonate and agitation. You could even make the Nitric Acid-free Silver Nitrate that's needed by dissolving 99.99% silver in good Nitric Acid. The secret to acid-free is to add only enough acid to dissolve 90% of the silver metal present (hood). One gallon of Nitric Acid will dissolve about 100 troy ounces of Silver. Boil at the end and filter. The solution is reasonable pure Silver Nitrate. The purifying of the silver is another story.

I have used Ni, Sn, and Cu Fluoborate baths, all with great success. They are acid and bond well to most substrates, without a strike, especially if you go in live. Their deposit characteristics are excellent, also. They use soluble anodes and operate near 100% efficiency. Copper is plated from a soln. of Copper Fluoborate only. Nickel has about 4 oz/gal Boric Acid added. Tin has 3.3 oz/gal Boric Acid and 20 oz/gal free Fluoboric Acid, plus some additives. The metal contents of the 3 range from 8-10 oz/gal. The pH's range from .2 to 3.5, depending on the metal used. Temps are from room temp. to 170F. Current densities are from 25-250 amp/sq.ft. Probably no agitation should be used.

If it were me, I'd play with this bath, in beakers. It might work great. It might not work at all. There may be some factor I'm not aware of.

In the late 60's, we had a customer that was using Silver DMSO baths to precision plate some critical electronic parts. I think they had a patent on the process. I think it worked great. It could be dangerous, though, since DMSO can take itself and other materials through the skin. I don't know the adhesion properties of Silver from DMSO baths.

Chris Owen
- Houston, TX, USA

Dear Mr Nurie,

From your knowledge of this supplier can you tell me

1. Would I be able to achieve a coating thickness of 7.62-12.7 microns?

2. Does the solution provide adhesion superior or equal to that of conventional cyanide based solutions?

The material I am plating is 12% Chromium Steel and can only have a Woods Nickel Strike and Silver strike prior to silver plating.

Nigel Gill, B.Sc. MIMF AIEMA MRSC
- Blantyre, South Lanarkshire, Scotland

You can plate directly on SS with ferrocyanide bath (nontoxic cyanide compound)!

Goran Budija
- Zagreb, Croatia

Goran Budija, is this Silver onto stainless steel using a ferrocyanide bath?

Ka-Ming Liu
- Toronto, Ontario, Canada Chemicals to silver make more shine [] 

i am industrialist.my job is to make silver wire more shine by less using silver.so my question is that which another chemical can i use to make silver more shine.

jariwala vinod
businessman - surat,gujarat,india

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