Preserving a nice coin

Corrosion is an endpoint. A normal progression could be: fresh minted-->patina-->toned-->corrosion visible--> corrosion deep--> back to nature.

Shortest time is between fresh minted and patina.

Time will vary between stages due to many factors, primarily water and environmental chemicals exposure.

Looking at pocket change I can see corrosion on many cents that are very recent.

Jim

 

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Well that is certainly something I disagree with.
See the post on this page made by illini:
http://www.cointalk.com/t65610-2/

 

1 or 1000, does it not entirley depend on conditons?

1 or 1000, does it not entirley depend on conditons?

 

Tell the truth I like Illinis conserved coin better , even with the lighter spots , though I'd rather save a little more and get a problem free coin .
rzage

 

That statement is actually really hilarious. Corrosion starts from the INSIDE? Exactly how? Wow, good thing you discovered this brand new system of corrosion. I'll inform our structural department working on Nuclear Reactors so they stop using metals. :smile

 

Anywhere from 1 second to a million years. If no air, gasses, moisture, acids, etc. can get to a coin, and no dramatic changes in temperatures happens, it should last as long as there is an Earth. I've seen coins that were only one year old look like something that was made in BC. Contrary to that many of my coins have been in my possesion for well over 60 years and no corrosion. Completely depends on the coins invironment and methods of existing there.

 

Sighhhhhhhh.... OK there is another way to get the corrosion out from the inside out. Ionize the sucker. Traci

This is for you CARL !!!! (AKA. Homer Simpson)


Caring for your Copper, Brass, Bronze and Other Alloys


Egyptian lamp holder, 1468-96. Museum no. 109-1888. (click image for larger version)

Problematic copper corrosion tends to form in spots that create pits in the surface. Sometimes the surface of a bronze object may look intact, but will have a pimply appearance - if you remove the surface over the spot you might find a corrosion pit containing light green powder.
If left untouched, the pit will gradually get deeper and larger, and may eventually burst, revealing the corrosion below. *****
The most active and rapid form of copper corrosion is known as bronze disease. This is caused by chlorides, which are particularly aggressive corrosive agents (e.g. salt, which is sodium chloride). This corrosion process, once initiated, will proceed quickly, forming a rash of spots which burst, spilling out light green copper chloride. These corrosion products will then cause more corrosion to occur.
Bronze disease is rare and is mainly seen on archaeological copper alloy objects that were buried in salty soils or were in contact with sea water. If you notice spots with a bright greenish powder emerging, consult a conservator since, whether or not it is bronze disease, it is best dealt with by a professional.

 

I was wondering if since this is a rare condition,does it apply to modern (within 200 years) coins? One would suspect that archeologic copper is made with substandard mining and refining techniques and more susceptable to this type of corrosion, being that is is near salty sea bodies. Our coins are not as one would suspect stored near salty sea bodies, which might in turn negate this possiblity of corrosion; and also offers itself no consideration in this realm of conversation. Sure it's possible on ancient antiquities but even then it is rare. Why not state something that is more likely? To prove a point that it exists?

 

Uniform or General Corrosion

The metal loss is uniform from the surface.
Often combined with high-velocity fluid erosion, with or without abrasives.
Pitting Corrosion

The metal loss is randomly located on the metal surface.
Often combined with stagnant fluid or in areas with low fluid velocity.
Galvanic Corrosion

Occurs when two metals with different electrode potential is connected in a corrosive electrolytic environment.
The anodic metal develops deep pits and groves in the surface.
Crevice Corrosion

Occurs at places with gaskets, bolts and lap joints where crevice exists.
Crevice corrosion creates pits similar to pitting corrosion.
Concentration Cell Corrosion

Occurs where the surface is exposed to an electrolytic environment where the concentration of the corrosive fluid or the dissolved oxygen varies.
Often combined with stagnant fluid or in areas with low fluid velocity.
Graphitic Corrosion

Cast iron loosing iron in salt water or acids.
Leaves the graphite in place, resulting in a soft weak metal.

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