Plating Surface Corrugation

That is really good insight into one of the criticisms of the plating.

There is another step in the process used to make the plated planchets. It's apparently an ARTAZN trade secret as to how it is done, but the plating is double thickness on the edge. Whatever the process, this step may be worth considering in the analysis. There is also some indication that the plating thickness may have been increased after the date of the following report. If so, the date of the coin may be an additional factor to consider. Here is the report information.

The Final Report, Alternative Metals Study (for circulating coinage), submitted to the US Mint by Concurrent Technologies Corporation under Contract Number TM-HQ-11-C-0049, 2012.

The double plating on the edge is mentioned in other materials. There is a mint report on it somewhere, and the Jarden/ARTAZN website mentioned it at one time. I can try to search for my materials on this. It is the edge itself, and not the surface near the rim, that has double plating.

I thought of two more things to consider. First, unlike other planchets, the mint does not anneal the zinc cent planchets before striking. Annealing is done by ARTAZN, but when and how in their process seems to be another mystery. Second, some of the zinc cents were in the toxic soup of the flooding following Hurricanes Katrina and Harvey. Some of these survived and were acid cleaned to return them to circulation. Broze cents that went through this cleaning have a readily identifiable orange tinge, even in circulation today. I haven't seen enough of the surviving zinc cents to have a good feel for what the treatment did to them.

This sounds problematical to me. I cannot imagine how it would be accomplished in a barrel plating process where the planchets are tumbled in a barrel with electrolyte!

I hope you can find the reference!

Thanks for the input/dialogue!

Researching plating has been fun, and also:

Fascinating

Frustrating

Challenging

I keep finding more alleys to explore and more lines of research to check!

So far, I have 2 more papers to share = one on Plating Cracks and Splits and one on Proof Cent Plating.

The Mint has been of some help but is withholding information on some questions. I am considering a FOIA request, but suspect a response under Exemption 4, which protects action obtained from a person that is privileged or confidential trade secrets and commercial or financial information.

1. Unable to answer this - I cannot think of a way to gather the data required for a proper answer!

2. One of my unanswered questions is the effect of the strike on a planchet with corrugation. To me, it is counterintuitive that a strike would not completely obliterate any existing ridges and valleys.
However, you make me think of one experiment that Ken Potter and I worked on jointly:

We were working on Rockwell Test Marks. See my paper from some years ago here: https://conecaonline.org/rockwell-h...ncoln-cents/

I had a Rockwell Test performed on a cent. That it was done after the strike is evident from the pressure ridge around the mark - a strike will obliterate it. It turns out that a strike does more - it deforms the mark extensively! Ken took that coin some years later and had it struck into his 50th Anniversary of Serving Collectors Medal. The following photo shows the effects of that strike. Notice that the surface of the field of the coin is NOT totally flattened, which I would have expected it to be! This tells me that the Ridges and Valleys are quite capable of surviving the strike!



3. I have seen no studies that mention the oxidation of the substrate beneath the plating.

Fascinating! Thank you! I hope it will be okay if I use your photos, should the opportunity arrive!

Looks to be a fine example of plating cracking and peeling!

Some TPGs might call this a lamination because they usually do not use the numismatic definition of lamination which is separation of an alloy along horizontal planes of weakness. I think they are in error!

Nice example!

Yes! Please do! Thank you!