If Silver Doesn't Corrode What Happened To This 1959-D Half Dollar?

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Author	Replies: 11 / Views: 970
MachinMachinMan Pillar of the Community Australia 1985 Posts	Posted 10/26/2024 11:32 pm Is 10% copper all it takes for corrosion to set in? Edited by MachinMachinMan 10/26/2024 11:35 pm Report this Post to the Staff

spru Bedrock of the Community United States 12477 Posts	Posted 10/27/2024 04:28 am Silver and copper both corrode, but it's not red when they do. My guess is that there was something iron-based on the coin's surface that then oxidized. In Memory of Crazyb0 12-26-1951 to 7-27-2020 In Memory of Tootallious 3-31-1964 to 4-15-2020 In Memory of T-BOP 10-12-1949 to 1-19-2024 Report this Post to the Staff
ijn1944 Bedrock of the Community United States 19109 Posts	Posted 10/27/2024 07:01 am Agree with spruett001. Report this Post to the Staff
nickelsearcher Moderator United States 15384 Posts	Posted 10/27/2024 07:13 am Where did you hear that silver does not corrode? Of course it does. Take a look at my other hobby ... http://www.jk-dk.art Report this Post to the Staff
Sap Moderator Australia 16805 Posts	Posted 10/27/2024 08:38 am Silver is corrosion-resistant, but not corrosion-proof. Bury a piece of silver in the ground and it will - slowly - start to turn back into the piece of silver ore from whence it came. Gold is "corrosion-proof" in terms of normal Earth-surface conditions, but can still corrode under certain chemically unusual circumstances. The 10% copper content of US coinage silver (or the 7.5% content of sterling silver) does weaken the resistance to corrosion as a whole; as a general rule, alloys are always more corrosion-prone than pure elements. Some alloys (like stainless steel) may appear to be more corrosion-resistant than their pure-element counterparts, but that's because the alloy is designed to oxidize very quickly, and this oxide forms an airtight layer preventing further oxidation. For this coin, I'm seeing two different corrosion effects: the brown, from (presumably) environmental damage, or perhaps fire damage. Second, we have PVC damage, in the form of the green goo seen around the rims. Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis Report this Post to the Staff
Coinfrog Bedrock of the Community United States 94367 Posts	Posted 10/27/2024 10:45 am Very good analysis. Report this Post to the Staff
smauggie Valued Member United States 271 Posts	Posted 10/27/2024 12:25 pm It really depends what you mean by gold. If you mean pure .999 (or .9999) fine gold, it does not corrode or develop a patina. Impure gold such as that in US coins, jewelry, etc, can develop a light patina which does prevent further deterioration. The patina is very similar to the color of gold and is next to impossible to visually determine on purer (18k+) gold. Report this Post to the Staff
cladking Pillar of the Community United States 2270 Posts	Posted 10/27/2024 6:02 pm Everything degrades in time. Some things are far more stable than others. Copper hydroxide becomes copper oxide, vaterite; calcium carbonate and gold given sufficient time will become auric sulfate or some other product of degradation. Silver is much more reactive than gold and copper much more than silver. Francium-223 undergoes radioactive degradation at a rate of half its mass every 22 minutes. Nothing lasts forever. Some environments cause much faster disintegration than others. Time don't fly, it bounds and leaps. Report this Post to the Staff
MachinMachinMan Pillar of the Community Australia 1985 Posts	Posted 10/27/2024 8:24 pm Interesting analysis guys. Just never seen a "rusty" silver coin before. Report this Post to the Staff
jbuck Moderator United States 187446 Posts	Posted 10/28/2024 09:19 am Great question and excellent discussion. Coin Collector Since 1978 Avatar Old Avatar 7070 Eisenhower Australia Canada World CCF Members on eBay CCF eBay Search Engine Report this Post to the Staff
jpsned Pillar of the Community United States 2200 Posts	Posted 10/28/2024 10:29 am I enjoy reading comments from people who know what they're talking about! Report this Post to the Staff
Dearborn Moderator United States 94636 Posts	Posted 10/28/2024 11:17 am Quote: I enjoy reading comments from people who know what they're talking about! That is why I didn't have a comment here Collecting since 1972. Learning from then on "Tell me and I forget. Teach me and I remember. Involve me and I learn." - Benjamin Franklin 7070 type set coin count: 51/76 Uncirculated American Silver Eagles My American Silver Eagle Proof Collection Sacagawea Dollars Innovation Dollars Eisenhower-Dollars Kennedy-Half Dollars Washington-Quarters Roosevelt-Dimes Buffalo-Nickels 1938-2005 Jefferson-Nickels Lincoln-Cents Report this Post to the Staff
	Replies: 11 / Views: 970

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