Lincoln Cents And Zinc Rot?

I have noticed that an even half way decent zincoln is getting tough.

I suspect the reason that coppers are fairly steady at 5% is that the zinc coins are rotting faster than the coppers are being hoarded. The cost to the taxpayer for this nonsense is very high.

It's not so much the dreaded rot that is increasing so much since once they start rotting, they don't last long. What's increasing is the black spots that appear on brand new coins. I coincidentally had three nice Gems on my dresser yesterday received in change ('18, '18-D, and '19-D) and all three had horrible black spotting. The '18(P) wasn't quite so bad.

They all get black spots, you can smell them, they stink. Zinc is a really good protector, you see it on ship screws. But zinc pennies have always been spotty looking to me. Due to the thin copper coating they will catch whatever the other copper or zinc coated copper coins have going on.

Just a few thoughts and rants. We have a long history of poor substitute metal coinage. The zinc plated steel cents rusted when the thin zinc layer quickly wore in circulation. The wartime nickels were too soft, and wore quickly. The copper plated zinc cents have a thin layer of copper on the obverse and reverse, which is problematic, but a double thickness layer on the edge, which works better. The brass-manganese-nickel dollar coins have the same rapid ugliness as the zinc cents. The only long-lasting and successful substitute metal coinage is the cupro-nickel-clad coinage (and its cousin, the briefly used silver clad half dollar coinage).

The problem with the cents is the bonding of the thin plating with the zinc. Zinc oxidizes quickly, which creates a protective layer. That's a good trait, because it protects what lies beneath. That makes it a perfect galvanizing metal for steel, for example.) Jarden Zinc makes the cent blanks, using a proprietary plating method that double-plates the edges and single-plates the surfaces. IMHO, three issues appear to exist:
The zinc core thinly oxidizes before plating. This places the zinc oxide in contact with the bottom of the copper plating, as well as normal oxidation from the outside surface. The plating is too thin on the coin surfaces to withstand this two-pronged attack. The edge plating is thicker, and better resists this issue.
The upsetting mill conversion of a blank into a planchet comes after plating. The resulting metal stress affects the surface plating near the proto-rim. This is a common area for deterioration.
The planchets are soft enough to be struck without annealing. The force of striking weakens the copper surface plating at stress points, particularly the raised lettering and more sharply defined devices. This is the most common area for deterioration.

Canada experimented with copper plated zinc cents, as well. The Canadian cents do not show the level of deterioration seen on the U.S. copper plated zinc cents, though they do show the same ugliness from loss of detail and surface discoloration. Canada also used copper plated steel cents toward the end of its production run of one cent coins. These coins fared much better in circulation, partly because copper bonds much better with steel and partly because Canada ceased production of one cent coins soon thereafter, and the coins did not circulate as heavily.

On a positive note, the massive unnecessary supply of zinc cents guarantees a supply of zinc oxide for retro sunburn cream for lifeguards' noses for many endless summers.

Is it possible that some 1980 Lincoln Penny have zinc rot due to mint trials?

No, zinc planchets did not exist in 1980.

to the Community, Hamsterbytes!