Re: Which Australian coins are most affected by sitting in vinegar?

David you are on the right track.

Try it and see.

Best use white vinegar (rather than brown vinegar, malt vinegar, cider vinegar) 
because that is almost a simple solution of acetic acid in water. The others have 
rather more organic minor constituents which probably will not get into the act, 
but just might. Apologies to non-Aussies -- I do not know what names and 
varieties vinegar is sold in elsewhere.

Find out the composition of various Australian coins -- try the website of the 
Australian mint for starters. Coinage metals are usually chosen so that coins do 
not react much with the sort of things they might encounter in the ordinary 
environment. You would not want your change dissolving if it came up against your 
fish and chips packet ;-)

Vinegar is a dilute solution of a very weak acid. Acids react with some metals 
and not with others. Find out a bit more about that from a chemistry textbook. 
Acids as weak as vinegar do not react much with metals anyway.

Do not be too surprised if none of the coins are affected much at all by vinegar. 
Sometimes experiments just work out that way.

An afterthought: vinegar is a moderately good solvent for body grease and the 
like. It might appear to do quite a bit by cleaning up dirty coins, even if it 
does not react with the metal.