Question

The thing is that all the other question talk about cleaning silver with aluminum foil and carbonated water. The recipe I use though is to soak the silverware and the aluminium foil in salt water (simply mix table salt and cold water). I got the idea many years ago watching a commercial for a product called "SilverStar" or something like that on TV-Shop which was essentially a 0.5 cm thick aluminium plats which you were supposed to but in a bowl with saltwater and all your jewellery and it would magically become polished. The explanations for the "recipes" using carbonated water are all along the lines that the acid dissolves part of the aluminum and then the aluminum ions in solution somehow react with the silveroxide.The question then is if I only use table salt and (still) water will the chemistry be more or less the same but only much slower (relying on CO2 dissolving in the water from the air) or is there something else going on? My understanding of what was happening with the salt water was that the salt water acted as a "wire" and the aluminium acted as the "sacrificial metal" in a Cathodic Protection. I always thought that you could essentially put the aluminium in one bowl and the silver in another and connect them with a copper wire.

So the question is twofold
1. What is the purpose of the table salt in my recipe?
2. Is there any (chemical) difference between "my" recipe with table salt and the more mainstream one with different flavours of carbonated water?

Answer 1

Table salt in the recipe serves as an electrolyte that facilitates an electrochemical reaction between aluminum and tarnished silver, with aluminum being the sacrificial metal. The saltwater allows ionic flow, acting similar to a wire in cathodic protection. Carbonated water contains carbonic acid, which might dissolve the aluminum oxide layer and accelerate the tarnishing reversal process compared to just using saltwater.

Step-by-step explanation:

The purpose of table salt in your silver-polishing recipe is to serve as an electrolyte that facilitates the electrochemical reaction between the aluminum foil and the silver. In this reaction, the aluminum acts as a sacrificial metal, whereas the silver tarnished with silver sulfide (Ag2S) is reduced back to silver metal. The chemical process at work in your method and the carbonated water method involve a redox reaction where aluminum is oxidized, and the silver sulfide is reduced. However, the presence of carbonic acid in carbonated water could potentially accelerate the reaction compared to just using saltwater.

The table salt in the solution allows the flow of ions, which is required for the redox reaction to occur. When connected by a wire or immersed in the same solution, a current can flow and facilitate the transfer of electrons needed to reverse the tarnishing of silver. In essence, the saltwater acts as a 'wire' in the solution, allowing the electrochemical reaction to happen, similar to cathodic protection.