How to Strip Plated Silver Off Copper

A. Alfred,

Electroplating, as in a process requiring a power supply, is not involved. The process is essentially the same as immersion plating. Zinc metal powder can be used to precipitate silver, as a metallic powder, from many different solutions. It is basically an exchange process. Silver and zinc switch places. The metallic zinc dissolves and the dissolved silver precipitates as a metal. Theoretically, I'm thinking that 1 g of Zinc will drop about 3.4 g of silver. However, if the solution contains chemicals that will dissolve zinc on their own, additional zinc will dissolve until this chemical is consumed and only then will the silver start dropping. An example of these chemicals, in this case, would be free nitric acid in an acid solution or a lot of hydroxide or free oxidizer in a cyanide solution containing free cyanide.

If you search for "electromotive series" (EM series) on the internet, you will find a chart which has the more active metals, such as magnesium, aluminum and zinc, at the top (usually - sometimes, but not often, the chart is reversed), and the less active metals, such as gold, silver, and copper, at the bottom. The general rule is that a metal in metallic form will drop out in metallic form, any and all dissolved metals that are below it on the chart. This assumes that the more active metal is soluble in that particular solution. There are also other peculiarities that can hinder certain combinations from occurring.

When silver in in a nitrate acid solution, you are much better off using copper than zinc to drop the silver. The main reason is that copper is right next to and above silver on the EM series. Therefore, it is very unlikely that there would be any other metals between copper and silver that would drop along with the silver. With zinc, which is far above copper, there are many other possible metals that might drop along with the silver - lead, cobalt, nickel, iron, e.g. Instead of copper powder, I would use a pure copper bar, the best being clean, scrap bus bar with no solder or plating on it. With copper powder, you are very likely to contaminate the silver with copper, unless you know exactly how much silver is in solution and use exactly the amount of copper needed to drop that exact quantity of silver. Almost impossible to do. With bus bar cut into lengths long enough to stick up out of the solution, so you can easily remove them, you can achieve a purity of 99+% silver, with very thorough rinsing.