Coin Word article on bubbles in cents

[Robert]

On page 99 of the Sep 1 Coin World is an article pointing out just how temporal the modern zinc cents are. They (correctly) point out that coppper plating of the zinc core sometimes causes blisters to appear just below the surface of the coin. It's an indication of the relative instability of the zinc-copper interface. The article also correctly says that zinc can oxidize into a dark, powdery substance.

This bubbling appears to be less of a problem now than in years past but the problem still does arise.

What will these coins look like 20 years from now?

How hard will it be to find truly "gem" zinc cents from the 1980s?

What's the best way to preserve zinc cents?

Does anyone know the chemical principle behind copper-zinc corrosion?

[coppercoins]

I don't know the chemistry, but I can say a few things...

1. The cents with corrosion, holes, blisters, etc. probably won't last another 20 years. They are being literally eaten up by the environmental conditions (air).

2. I heard that they improved the technique of coating the zinc planchets in the late 1980s, which is why you're less likely to see this problem on a more modern cent.

3. The corrosion and disappearance of the earlier zinc cents is going to be felt, and quite a bit. Some rolls from the early to mid-1980s are already skyrocketing in BU, and will likely continued to do so. I would expect a 1986P roll to shoot through the $100 mark by the end of this decade.

[GarryN]

They have to do something about the cents because they look pretty bad in general. Same with the state quarters. They look fine at arms length, but when you put them under the scope, the surfaces are not very good.

[coppercoins]

That all has to do with the crappy, cheap method they use to mint coins now. Since it costs them much less than minting coins the right way, I highly doubt you'll see any real difference. My idea would be to go to nicer, deeper designs that require multiple hubbing for collector's sets (mint and proof sets) and keep the crap for circulation. Even that won't happen because of expense. It's a lose-lose situation. We lose quality coins and they lose collectors because the new coins have no appeal.

[cladking]

So long as the copper plating stays intact these coins are fairly stable. Of course copper is very reactive and many of these cents have been made with bad plating so there is and will continue to be a high rate of attrition. I recently went through a bunch of 1984 mint sets and was appalled at what I saw. The coins in mint sets are typically the best of the best in virtually all regards but the planchets are at best only slightly better than for the coins intended for circulation. The Philly coins were poor with about half of the coins spotted or on inferior plabnchet. Those which were undamaged usually had other problems like excessive marking or poor strikes. The Denver coins were dreadful. These coins have been "turning" in large numbers in the last few years. Large percentages of them have black spots ranging from quite small to much of a side. While these are better struck on better planchets than the Phillys, they are disintegrating. Only about .75% still go superb gem or better. Even the gems are getting few and far between. If the rolls are at all like this then nice '84-D's are already tough. It's interesting to note that about three quarters of the Denver mint tokens in this set is already spotted. I dread checking the '84's in my safety deposit box. These should fare at least a little better since they've already passed tests for quality, but it's a certainty that some have turned.

[cladking]

Copper oxidizes into a green rust and zinc into a white one.

The coins should be stored in low humidity and constant temperature conditions.