Of course coins corrode.
Over time coins corrode.
They corrode faster in tap water.
Bleach also corrodes coins.
If you have time, try some experiments and see what substances corrode coins.
they do
In a normal atmosphere, a coin has a very thin layer of a metal oxide covering it, which prevents any sort of degradation by external forces, as this layer is very chemically inert. This layer is...
salt water
Coins show more corrosion when they are in tap water.