Does Silver Corrode?

Silver, like the vast majority of metals in the world, corrodes over time. Tarnish is corrosion that develops on silver, giving it a colour that is somewhere between brown and bronze. The bad thing about silver corrosion is that the corrosion layer is unappealing to collectors, which could actually lower the value of the silver product. So why does silver corrode? And can tarnished silver be cleaned? Let’s jump in to find the answer.

4Ag + H2S + O2 —-> Ag2S + H2O

The process by which the silver corrodes is described by the equation shown above. Silver reacts with hydrogen sulfide (H2S) and oxygen (O2) to create silver sulfide (Ag2S) and water (H2O). This is a simple equation: silver will start to tarnish when exposed to hydrogen sulfide and oxygen in the air. This is why silver rounds and coins need high-quality capsules to limit their exposure to air. In rural areas, the concentration of hydrogen sulphide in the air is between 0.00011 - 0.00033 parts per million. Meanwhile, the concentration could go up to 0.001 parts per million in the urban area. The H2S concentration could be even higher in the industrial area. It’s safe to assume silver will corrode faster in the area with higher ppm of H2S.

We have now understood the cause of silver’s tarnish. On the other hand, according to the accepted scientific theory, sterling silver should tarnish more quickly than fine silver bullion. A silver product known as sterling silver contains 92.5% silver in addition to other metals. 7.5% of the other metals have a higher potential for corrosion as compared to pure silver.

Removing Tarnish

1)Take a huge glass bowl and fill it with water
2)Toss in a pinch of salt and a splash of vinegar. To make a uniform solution, fully combine them with water.
3)You need a large piece of aluminium foil large
4)Soak this aluminium foil entirely in the bowl.
5)Drop the silver products in the solution so that it is resting on the foil.
6)For the next hour, don’t touch the container.
7)Take the silver out and give it a good rinse.
8)Wipe the area down with a dry cloth.

3Ag2S(s) + 2Al(s) → 6Ag(s) + Al2S3(s)

The above is the chemical equation for cleaning the tarnish of silver. As you can see, no silver is lost in the process. The Silver sulfide (Ag2S) reacts with aluminium (Al) and produces pure silver (Ag) and aluminium sulfide (Al2S3). You can throw away the remaining Alumiun sulfide and the solution.