Hi my chemistry is pretty dire but have vague idea that an electrochemical cell could be used to remove soft solder (lead/tin probably) from a piece of sterling silver in need of a repair.

The correct electro cell arrangement could be a good method of removing contaminants without damaging the silver / copper of the piece since lead and tin are less noble...

Opt 1 (reverse electroplating): Cell with something like a weak sulphuric acid solution as electrolyte, the contaminated silver as cathode, and possibly a stainless/carbon anode. Current should cause oxidation of the soft solder to lead/tin sulphate in solution. I'm guessing lead/tin may build up on the anode where would also be a release of... er, oxygen???

Opt 2 (Conversion to lead/tin chloride): Cell with something like H2O / NaCl solution as electrolyte, the contaminated silver as the anode and carbon / stainless cathode. Current should cause Cl to liberate at the anode and bond with lead / tin which hopefully will dissolve in the solution or can be scraped off easily. (not sure this is any better than just pouring HCl onto piece though!)

Opt 3 (conversion to lead/tin oxide): Cell with pure water or weak NaOH solution as electrolyte, the contaminated silver as the anode, and a carbon/stainless cathode. Current should generate oxygen at anode which might also cause lead/tin to convert to oxides which can hopefully be scraped off easily.

Are any of these methods viable/preferable? Opt 1 seems to be best as i dont think the electrolyte will react with the silver/copper if not too strong. Not sure if the sulphates will go into solution though or just build up / precipitate out from cathode.

Are any of these methods likely to be preferable to just pickling the piece in acid such as HCl?

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    $\begingroup$ I know I'm not supposed to give my opinion on here, but you asked..I would go with option 2. The HCl won't do anything (not dissolve copper anyway).This is tough to answer because the way the options are phrased is confusing... $\endgroup$ – KASEY Apr 11 '19 at 12:32

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