Do you mean that green verdigris which eats pits into the coins? If that's it I understand an olive oil soak for a few months will stop the advancement, but as you know it won't undo any damage. Take Care Ben
Nothing will reverse it but a dry environment (the dryer the better, the corrosion requires water to proceed and water vapor in the air will work just fine) with stable temperatures will prevent it from progressing. Vinegar is just acetic acid so all that would accomplish would be to soak your coins in acid. Not a great idea.
Are you sure it is corrosion? Try describing it's appearance such as color, amount, dates of the coins in question, etc. Note that there are many different types of contaminates on coins on different types of coins for different years where the material of the coin itself is different. In most instances if the so called corrosion is a chemical attack on the metal itself, removing the contaminate will remove some of the coins metal. I suggest you don't try to remove it unless you know what your dealing with. Place such coins in as much of an air tight container as possible and the reaction should stop but the present situation will remain. If the coins are not very valuable you may want to experiment with such things as Acetone or other such chemicals, however, again I suggest you not to mess with them since may end up doing more damage than good.
Below is an image of the corrosion. If the images doesn't show try: http://xs313.xs.to/xs313/07106/1892o.tiff.png Note the corrosion is mainly on the right rim. The damage has eaten slightly into the metal. What would be the best way to remove/stop the corrosion without removing the toning? Should I just leave it alone? I considered using a fine paint brush and "painting" a dip onto the affected areas. Let me know your thoughts.
If you use a dip it will remove patina and looked dipped. Also you don't ever want to leave the dip chemical on your coin but for a few and I mean few seconds and then rise throughly. If that was mine I would soak in olive oil for a few months and then try your soft brush to expel and green matter. Take your time and learn what you can before you try anything. Remember you can only screw up once on this coin. It a beautiful coin by the way!!
The coin appears to have PVC damage. I would recommend soaking it in pure acetone to remove the PVC contamination and then rinsing it thoroughly in distilled water. If it is PVC, and I'm pretty sure it is, it will only get worse if not removed.
How long do I let it soak in acetone? Where do I get acetone? Does acetone affect the toning? This is a proof that currently is in a PCI holder. Under magnification the corrosion has eaten into the coin just a little and it has a seafoam green color that looks like what you would on a battery terminal. What are the tell-tell signs of PCI damage. I always thought it was a green slime???? I really want to save the toning, but dont want a corrosion leaching the coin. Here is there reverse: http://xs313.xs.to/xs313/07100/1892Rev.tiff.png
A very few seconds, followed by repeated rinses in fresh distilled or de-ionized water, and air drying on a soft cloth, no rubbing!. Any paint, hardware or home center store. Be sure to get the pure stuff and stay far away from nail polish remover, which has unknown additives. Some people thinks it affects tarnished copper, but it's pretty universally agreed that it is harmless to the tarnish on silver or cu-ni. Acetone won't restore the corroded part, but it will prevent further corrosion. That's typical PVC damage Haze and slime are just different stages of PVC contamination. Usually there's no corrosion beneath haze, and usually there is corrosion beneath slime.
Will the corrosion just disolve leaving pits after the acetone dip/distilled water application or will I need to use a fine paintbrush to remove any leftover corrosion? Thanks everyone for all your help.
If the PVC damage has advanced to the point of corrosion, there is absolutely, positively, without doubt or exception not a thing you can do to reverse it. Once the metal has been affected, it can't be brought back. "Fine paintbrushes", camera lens brushes, toothbrushes brass brushes, and even cotton swabs or Q-tips, are all going to leave scratches if they are used. The only difference will be in how deep and noticeable the scratches will be. As posted above:
I was considering using the paintbrush to lightly "dab" the affected corrosion areas with acetone followed by a rinse and airdry. Understanding how delicate the surfaces are I thought by dabbing the affected areas would keep me from having to submerse the coin in an acetone solution. Personally I dont like 100 year old coins that are pure white and shake my head at coins that have been cleaned. Since I have never used acetone I am trying to be as delicate as possible. Definantly will need to find a cheap nickel with corrosion to test this on. The only noticable loss of metal willl be on the rim.....hopefully. Thanks again
