The authoritative public forum
  for Metal Finishing since 1989
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Electropolishing of silver

Q. Hello, and thanks in advance for any advice about electropolishing that you can give. My partner and I run a small jewelry company in Mississippi (www.Xover0.com) We work primarily in 925 Sterling Silver. As you can see, we have some nice inner-geometry intricacies going on, for which we could use electropolishing generally. However, we are about to do a piece which for which our mechanical finishing just won't work at all.

We've tried piecing together an electropolishing setup. We started with this video, which is for Stainless:

After reading as widely as we could and getting advice from a chemistry prof (this is not his area of expertise) we figured out how to use commercially-available 37% sulfuric rather than 95% concentrate which we can't get.

So our electrolyte mix was 108 ml battery acid ⇦this on eBay or Amazon [affil links] , 292 ml phosphoric acid 85% ⇦this on eBay or Amazon [affil links] . In other words, we have a mix that is 62% phosphoric, 10% sulfuric, and 28% water. Early reading also told us to put a MINISCULE amount of thiourea in (about 1g / l) but we've since found out that this is bunk and are now running 20g / liter.

Having nowhere else to start with the electrical side, we started with that guy's voltage / amperage settings. And basically dissolved a piece in our mix. So we bumped back down to as low as 0.16A and 2v, as high as 4v and 0.4A. We can notice the pitting getting worse faster at the upper end, but it still doesn't work at the lower end. We still get pitting even at 0.2A and 2v, in as little as three minutes.

We've tried both a large and small titanium cathode, the anode connected to the piece is a titanium rod. The distance between is typically around 2". We're agitating the mix and running between 50 and 70 °C in all cases.

We have heard that adding glycol as a thickener can help, but we haven't tried that yet.

We would love any advice you guys can give on a good electrolyte mix and electrical settings (and temp if it's a big difference maker) for successful electropolishing of 925 sterling. Thank you in advance, and thanks for what is clearly a committed bunch of experts and enthusiasts in finishing - keeping human expertise on an internet where that is dying by the day!

Duane Robot
- Starkville, Mississippi
November 10, 2024

Ed. note: Since 1989 this forum has enjoyed the camaraderie & warm aloha which real names & locations afford. If you're not into that spirit, those who do post with their real name may be less likely to engage with you.

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⇩ Related postings, oldest first ⇩

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Q. I'm looking for an electro-chemical polishing bath (composition or commercial) available for silver?

P. Berger
- Netherlands
1998

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Q. What commercial processes are available today, and from whom, which will allow extremely fine polishing (finishing) of silver coating down to several microns? An Israeli firm is seeking info on deposition technology to avoid waste when applying a silver coating to a surface that is not smooth to very high standards (by microscopic analysis). Current electropolishing is not to a satisfactory level and more stringent standards are desired for implementation. Any suggestions would be appreciated.

avigdor ben-dov
- Israel
1998

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Need Electro-glo 200

Q. I wish to electropolish precious metals, mainly silver. A product called Electro-Glo 200 has been recommended, but I can't find the Electro-Glo Company, which was in Chicago. If they're still out there, I'd like to know.

Alternatively, is there another product I could use?

Nelson D. Durie
- Ottawa, Ontario, Canada
1999

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Will silver etching, electropolishing, or electroplating work best?

Q. Hi,

The problem is as follows: the composite silver-ceramic material is produced in the form of the tape, so that the silver sheet is enclosing the ceramic material. This material is then rolled. Could anyone give me a suggestion as to how to remove the silver surface, and in the same time to preserve the grain boundaries? So that the texture measurements could be done on the interface Ag-ceramics, or only the ceramics.

Etching with the mixture of NH4OH and H2O2 is too violent, rendering pitted surface, NH4OH and HNO3 is producing the same result; electropolishing is not working with complete damage to the Ag surface. Mechanical polish is not working due to the extreme softness of the silver. I was wondering whether the electrodeposition would work?

Thank you,

Predrag Kisa
- Pittsburgh, Pennsylvania, USA
2001

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How do I electro polish sterling silver charms?

Q. I have been told that we do not need to polish our sterling silver charms by hand but should be able to use electro plating and furthermore believe it is fairly simple to build a small system for ourselves - is this right? Help, we are not very techie and would appreciate some advice.

Regards,

John Goodridge
animal treasures - pet related giftware - Woking, Surrey, England
2006

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Polishing silver with least effort at home

Q. I am looking for a way to polish a lot of silver with minimal effort (not interested in Brasso and elbow grease). Being an engineer, I would like to try electropolishing, yet I have no information on how to do it or even if it would work. Can you direct me to this information? Or maybe you know of a "Handyman" method to do it at home?

Jason Cook
1998