The Unique Conservation Challenge of Post-1982 Cents

Posted by David W. Lange, NGC Research Director on 6/23/2010

Many of the 1982-83 cents showed raised bumps from gas trapped between the layers.

The rising cost of copper in the early 1970s nearly resulted in the U. S. Mint converting to cents made of aluminum or brass-plated steel. Both issues were produced as trial strikes from dies dated 1974, but the crisis passed, and the coining of normal brass cents (erroneously called bronze) continued through 1981. The high inflation of the 1970s and early ‘80s, however, ultimately rendered their production cost prohibitive, and an alternative was again sought. The Mint determined that its most viable option was to go with cents of zinc that were plated with brass for a net copper content of just 2.5% (the larger message that the cent had been rendered obsolete by such inflation and should be discontinued altogether was somehow missed). The minting of brass-plated zinc cents began in the latter months of 1982, a year in which both the old and new compositions were struck.

The reverse of this high-grade and
valuable 1983 Doubled Die Reverse
Lincoln Cent shows a number of
small raised bumps caused by gas
trapped between its zinc core and
and copper coating.
click image to enlarge

While the zinc cents solved the immediate problem of finding a coin that cost less than one cent to produce, the resulting pieces were less than satisfactory when first mass produced. It took a lot of trial and error to consistently produce coins whose brass plating adhered to the zinc base properly. Many of the 1982-83 cents showed raised bumps from gas trapped between the layers. When compressed during the coining process, these gas occlusions formed tiny pimples that were unsightly and hinted at bigger problems. These soon manifested themselves when the coins entered circulation, as they quickly formed dark swirls on the brass surface. More seriously, the striking process sometimes flattened the brass plating so much that the underlying zinc was exposed. Since zinc is a very reactive metal when exposed to finger oils and other environmental triggers, corrosion became a highly visible problem. This was especially true at the coins’ peripheries and edges. Frequently seen today are zinc cents placed within albums or folders that have corroded from their rims inward, leaving their central areas bright and coppery. So pervasive was the problem of zinc exposure in these early plated cents that the Mint double plates its proof cents, because the greater pressure used to bring up details in a proof coin easily breaks through single plating.

The problem of trapped gas causing raised lumps and streaks continued in ever-diminishing numbers as late as 1986, and cents made since that time are seldom seen with this effect. Nevertheless, they are still susceptible to corrosion from their reactive zinc centers, and this becomes a very real concern for collectors attempting to preserve them in gem condition. The most simple step to take in assuring their long term preservation is to control the environment in which they are stored. Exposure to extremes of temperature and humidity is harmful to all coins, but it is quite a serious problem for brass-plated zinc cents and particularly so for the earliest issues.

NGC certification and encapsulation provides a very protective method of storage, and those cents graded by NGC since April 1, 2000 are covered by the company’s grading guarantee for a period of ten years. In combination with a stable storage environment, this should be enough to provide for the lasting beauty of gem cents. Even so, there remains a remedy for those coins which may have deteriorated due to mishandling or atmospheric contamination. NCS can perform conservation that corrects the effects of unattractive toning and minor corrosion, as well as removing any contaminants that may be adhering to a coin’s surface. Given the sensitivity of their brass surfaces, however, zinc cents having deep corrosion are not restorable to the extent that they may be numerically graded; such coins will be Details Graded, though they will likely be far more attractive than before.

Proper conservation of the sort performed by NCS can do much to remove undesirable contaminants and stabilize a coin’s surfaces for long term preservation, but this may not be a viable solution for coins of modest value. Unless they are in the top grades typical of Registry Sets, most post-1982 cents are not sufficiently valuable to justify the expense of conservation. Since they’re not rare coins in overall numbers, the best program then is to preserve them carefully from the outset to prevent environmental damage. But, for those coins which do need attention and are deemed by their owners as worthy of the expense, NCS conservation remains a safe and reliable option.



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