I was looking through a bunch of early date large cents I've recovered by metal detecting. While looking through them as well ad online pics I've noticed all are pitted or corroded by being buried. So I'm curious what else could cause these coins to be pitted/ corroded other than being buried.
the planchets were imported from england so they would sit in sea water for months. copper refining probably wasnt the same 200 years ago either.
People always seem to think that just because it was a long time ago that people back then didn't know how to work with metals or refine metals. Well, not much has changed really even with modern technology. Humans have been refining copper for thousands of years - longer than any other metal. They had no problems in that regard. But copper is also our most reactive coinage metal, it reacts with almost anything. Water of any kind corrodes it, minerals and acids in the ground corrode it, even exposure to the air will cause copper to corrode over a period of time. So the only unusual thing is when you find older copper coins that are not corroded.
So would that be in all states or would a ms 1793 cent usually have no corrosion, supposing that they exist.
Doug is very correct about the reactivity of copper compounds. It also should be noted that many metals including copper and silver can react slowly over a long period of time in a good environment to produce a patina that resists further corrosion of the base metal. Many ancient coins can show a patina with little corrosion beneath it for hundreds or thousand of years with perhaps a green coloration or mild toning in the case of silver. In some desert areas, coins in the sand can react with the silica to produce a very resistant patina. Sometimes today, rather rough cleaning is used for ancient coins, often destroying a protective patina, and todays atmosphere with sulfurous gases and acids from mans utilization of sulfur containing coal and oil can then rapidly cause corrosion in the presence of water/humidity. I predict that a modern coin will undergo further corrosion faster than a patinated ancient coin. Even in the US, the atmospheric corrosive contents today are much higher than in the late 1700s
Oh they exist, quite a few of them exist actually. And yes, even some of the MS examples have some pitting and bumps from corrosion. Look at the blow-ups of the coins found at this link - http://coins.ha.com/common/search_r...93 MS&Nty=1&N=51+790+231+307&chkNotSold=0&Ns=
Cool thanks for the link, it helps out a lot. I have a bunch of dug up early cents, and I cleaned up an 1801 that appears to have MS details but corroded, so I was curios to see if it could still be MS details. Thanks for the help extremely informative.
Hello I have an 1828 half cent that appeared to be in a higher AU great and to the right of the bust on the obverse in the field before the stars when I turn the coin in a specific way when it hits a light there is a mild green toning do you think that this may be the start of corrosion? Please keep in mind that it appeared to be in a red brown state. Also I like in a pretty humid place in north Texas but I keep the coin in a hard plastic case that has padding on the inside.
Yes, I would say likely it is the start of corrosion, but a photo would help for determination. It would also be good to know the history, how long have you had the coin, the type of holder it is in, do you think it has formed this color patch since you have had it, etc. Jim
Thank you, I would say that the color patch has formed science I had gotten it in collection I do not know much about its history other than I got the coin about a year ago at a coin show heres a couple of images this is the most that you will see it its in the field to the right of the bust.
All that is required to start the corrosion process is air. All air contains water and other contaminating gasses which react with metals. It comes down to one simple thing, the rate at which the corrosion process proceeds....it's not a matter of IF, it's a matter of WHEN. As collectors all we can control is the rate. It's impossible to completely protect coins. However, with proper storage techniques, we can make the process infinitely slow.
There is a product called VerdiCare that can slow the process and in some cases alleviate the damage!
