Dipping experiment.

SanctionII

Has anyone ever experimented on a junk type coin (i.e. junk silver dime or junk cent) by placing it in a dip and letting it remain there for an hour, day, week or month?

I am curious as to what would happen. Does the dip cointinue to eat away at the metal until there is none left or does it reach a point of stasis where no further reaction takes place and the coin remains in a specific condition, weight, etc.

If anyone knows about this, please favor us with your comments.

gyocomgd

Just guessing, but I'd think that eventually the coin would dissolve completely. It's the same metal through and through, and if can strip off a thin layer of the surface, logic would hold that it eventually would strip away everything.

solid

We need time-lapse photgraphy for this one!

Ken

fc

you would have to keep refreshing the liquid the coin is in.
it would eventually reach a neutral state and the reaction
would stop.

a strong acid might be more interesting.

ModernDollarNut

One thing for sure, even MS70 will start eating into a clad coin if it is left in a full strength solution way too long. Talk about ugly! Once the copper core can be attacked, things happen fairly quickly.... Overnight in full strength and I've seen SBAs turn a rough corroded black. MS70 is alkaline rather than acedic and not all that caustic but it still does a number over time. Rob

lkenefic

<< <i>Just guessing, but I'd think that eventually the coin would dissolve completely. It's the same metal through and through, and if can strip off a thin layer of the surface, logic would hold that it eventually would strip away everything. >>



The "best" way to disolve a penny (or so I'm told) was an experiment conducted looking at the corrosive properties of several acids in relation to Taco Bell Hot taco sauce...the Taco Bell sauce won hands down but it took a couple of months to disolve the penny...and I'm not certain if it was a post 1982 zinc cent or a pre-82 copper.

I could probably replicate this experiment in lab.....

Coindexter

The first coin I ever attempted to dip was a proof 1961 Roosie that had some minor rim toning. I don't know why I dipped it. I just HAD to dip something (newbie disease maybe). At any rate, I left the coin in the solution (eZest) for about a minute (which is at least 6 times longer than the manufacturer directs). On top of that I rinsed it improperly in tap water. The result is one of the ugliest coins on the planet - and the only one that will ever be made ugly by me.

Oh, BTW, the coin turned black and FDR looks like an alien due to the lack of hair and ear details.

xphobe

When I was a kid I found that after using a jar of dip to clean several silver coins, if you then dip a bright copper penny it will turn silver. I'm guessing some silver goes into solution but plates out on the copper, rather than the copper being eaten away. Not sure what kind of dip it was though. This was back in the 60s, before they had MS70.

Coxe

Depends on the ratio of reacting agent to the metal. Certainly it can only exhaust what it has on either side. Will there be a slowing and a near cessation in the reaction rate based on the build-up of surface material product of the reaction? Dunno. There must be a chemist or material scientist around here somewhere.

JapanJohn

Coin alloys aren't my specialty but I use to be a Materials Engineering Tech for Uncle Sam (US Navy and Marine Corps rep) in Aircraft Corrosion Control matters. We used acid solutions to chemically treat alum and steel for corrosion removal and for preparation prior to painting.

It's my experience from some lab work that usually a very small amount of metal will be removed in an acid dip or immersion. At some point at least with Alum the surface begins to "burn" (bad description) and the formation of a rough dark brown surface will form. In matters of corrosion removal it took significant amounts of time to remove metal and the solution would have to be changed or reapplied.

With steels you'd just turn the surface rust into something else that was durable and pretty corrosion resistant.

It's going to depend on the solution and the length of exposure but I think you'd have to want to dissolve a coin before you actually could. No doubt in my mind that acid treatments will remove strike details because the loss of metallics is certainly measurable. My experience lies mostly in hexavalent and trivalent chromium treatment products so take all this with a grain of salt.

Also the solution contained some potassium ferryacyanide and some bluish toning could usually be seen in a surface treatment because of the color of the hexavalent and the p.f.

John