Acid Damaged Coin?

It's real, but time-lapsed - the reaction isn't that fast in real life.

As for 47P7's questions on acid reactions with coins, the end result does depend on several different factors.

Yes, a shiny coin dipped in acid (and I'm including "coca-cola" or other carbonated soft drinks in my definition of "acid") briefly then washed thoroughly straight away will look fairly smooth and non-porous once it's done, because the acid eats away at all the surfaces at the same rate.

Pitting occurs when there is something to cause different rates of reaction. A circulation-toned coin is a good example of something that can cause this; the oxide layer is unevenly thick. The video shows a good demonstration of how this oxide layer provides some initial protection against the acid, as the initial reaction is much slower than the later reaction.

Another excellent way to create a pitted coin is to not wash off the acid properly, but just let it dry there. The acid becomes stronger in some places than others, eating away those spots. I learned this to my cost as a YN after seeing a science show on TV telling me how to make my copper coins shiny using lemon juice; they forgot to say "make sure you wash the coin thoroughly afterwards".

Silver is a more "noble" metal than copper, which means that copper and copper alloys are much easier to eat away with acids than silver. Weaker acids like coke and vinegar simply do nothing visible to silver. You can't use any chloride-based acid like hydrochloric either, because that quickly forms a silver chloride layer that stops further corrosion. Nitric acid, however, does the job on silver nicely.

The presence of the distinctive brown fumes towards the end of the video indicates that the acid used here is nitric, or perhaps a mixture of nitric with something else. Aqua regia, an acid mixture which can famously dissolve gold, is a mixture of nitric and hydrochloric acids.


No it's not. I can still see it.

And it shows all the hallmarks of a classic acid-attacked coin. "This a paper thin coin" is perhaps the most telling sign of all. It certainly is not a mint error and is not worth the hundreds being asked for it.

To quote from Star Trek IV, "Whoever said the human race was logical?"

As with any post-mint damage, some acid-attacked coins may have been made by accident. Car batteries contain concentrated sulfuric acid; an accident with a battery in a workshop or garage could easily see a pool of acid slowly flowing over a coin sitting on the floor, or down a drain that had earlier trapped a coin. Or a bottle of vinegar in the kitchen gets knocked over into the change jar. Or maybe a beach-combing metal detectorist decides to use acid to clean up their corroded finds to make them look more coin-like before spending them.

Others are simply human curiosity: the attitude of "I wonder what happens if I do this to this" has caused many serendipitous scientific discoveries and created many odd and curious artefacts down through the ages. Everyone thinks they're the first person to wonder what happens when a coin is dropped into cola. Or, in more modern times, they see a science-for-kids TV show or YouTube video and, wishing to test its veracity, decide to try to replicate the experiment themselves.

Some may have been made deliberately, for fraudulent purposes or otherwise. In some countries, counterfeiters might try turning a large low-denomination coin into a smaller, thinner but more valuable coin. Deceptive ebay sellers might offer them for sale to the gullible as "unique mint errors". Or maybe an artist wants to make a statement about the ephemerality of the monarchy.

Because the forum here provides the "what" (that is, the short answer). You want to know if something is post mint damage, then the members will tell you in about as many words, based on their experience.

Google, will provide you with the "why" and "how" (the longer answers you seek).

@ 47p7
For anyone who doesn't want to handle these chemicals ( or is to young to do so ) its easier and safer to go to Google or Youtube to observe what different acids do. Playing with battery acid is not a good idea. The more acid coins you see the easier it becomes to determine just what it is your looking at. Searching the internet is just homework that we have all done now its your turn. All the ways different chemicals attack different metals..its to much to list.
Spend some time searching this and you too will say - "acid coin IMO"

People who ask questions are trying to enhance their understanding, not a bad thing.
Some forum members have the answers at hand, this is a good thing.
I believe in helping one's self, but again that is what a forum of like minds is for, an exchange of ideas.
The fact that there are those at different learning levels is going
to create an imbalance. Meet the question with a forthright and true
answer. Put your information forward without editorial. Offer the
inexperienced a hand, we may stop asking the questions if met with
opposition to a query. Not everyone has access to the libraries of
which you speak. Not everyone has an interest in the hobby to the extent that some would hope.
I can google with the best of them, I come here for
the personal attention to detail and to ask and have answered specific questions.
Is there a problem with this?

Silver Don .. agree but I will say a couple of things. When you get the basic info from some stuff on this forum it can be great fun to further research the net or find stuff in a book sort of a like building a pyramid from the base up. Also my library of numismatic books is there for all to share. If I can possibly help anyone on this forum I will share to the best of my ability. Knowledge is the most powerful tool in numismatics and should be shared.

Pacificoin - I thank you for the offer of your numismatic library, I will take you up on that in the future. Cheers.

penneyman007 - I agree, a perfect balance is also a free flow of ideas, information sharing.

Fixguy - thanks.