Coin Collectors Question

[hoyaguru]

I have coins from all over the world in a box all mixed together. I went to sort them last night, and found a lot of them had turned brown/black with some sort of corrosion, I guess a couple different metals didn't get along. What should I use to clean them?

 

[huesmann]

sulphuric acid

 

[Crazymofo]

"CLR" cleans like no other!

 

[FritzTheCat]

Cleaning coins reduces the value. If you intend to sell the coins sometime in the future, don't clean them. If you are keeping them and are not concerned about resale value, try Tarn-X.

 

[vailr]

Coin shops may have "Coin-Solv" or similar cleaning products. Gently clean with soap & water first, as: the less cleaning, the better.
The corrosion is similar to the corrosion found on a car battery terminal.