Is there a fine line between toning and corrosion?

dan1ecu

When does a surface that is modified chemically go from being “toned” to being “corroded”? Are pits necessary for a coin to be designated as having corrosion? Can luster be used as an indicator of a surface that’s damaged by corrosion? I would think that most early coppers would have at least some corrosion/oxidation. Oxidation is the cause of copper turning brown, isn’t it? Where is the line drawn?

Dan

Placid

Pcgs defintition.
corrosion
Damage that results when reactive chemicals act upon metal. When toning ceases to be a "protective" coating and instead begins to damage a coin, corrosion is the cause. Usually confined to copper, nickel and silver regular issues, although patterns in aluminum, white metal, tin, etc., also are subject to this harmful process.

littlewicher

Will PCGS grade a monster toned coin with slight corrosion spots? I have a 1955 Jefferson Nickel, that is one monster, full blue. It has slight corrosion in some spots.

DMWJR

My understanding:

1. Toning is NOT a protective coating.
2. All toning is corrosive degredation of the surfaces of a coin.
3. If coin continues to "tone" the corrosion will eat into the metal.
4. The darker it gets, the more it eats.
5. The highest state of preservation of a coin's surface is for it to be just like the day it was minted. Toning is not included.

My opinion:
1. Don't buy copper with ANY toning. (Unless you are buying big fat circulated coppers). You can't stop the degredation, period.
2. Professionally remove light toning on silver coins.
3. Coins that have naturally toned near black will be pitted.

PS: I recently bought a MONSTER toned coin from TBT, thanks Bob. I knew what I was buying and bought it anyway. I like the coin, and it is the only "Monster Toned" coin I have ever bought. Any other coins I bought with toning are now white blazers.

wallstreetman

Toning is corrosion!

its4real

On the day copper is minted - it begins reacting with the oxygen in the atmosphere, ie, it begins corroding. It only goes downhill from there.

Higashiyama

Technically speaking, toning results from corrosion, but saying that toning and corrosion are one and the same is deceptive, since corrosion has a negative connotation, and suggests an ongoing degradation of the metal. Toned coins on the other hand, can be stable with little change for dozens of years, perhaps centuries.

Also, the situation differs depending on whether we are talking about gold, silver, or copper. Though a gold coin will tone, it is unlikely to suffer material surface damage from toning. Copper is the most likely to show surface problems commonly associated with "corrosion"

grip

I would think the small carbon spots that start on a coin ,either from liight moisture or even your breath will eat thru the patina and cause corrosion.I have seen many light toned coins that do not display specks/carbon,therefor I would think they will be around for some time without corrosion..Did I make any cent's.Al