Need Help Getting Rid Of Corrosion

[Zoomboi]

Hey guys, I have a coin that is made of nickel, but it has green corrosion from being stored with copper. I need to find a way to remove the copper corrosion without damaging the nickel. Thanks for any and all input.

[Vee]

Nickel does dissolve in nitric acid, but the concentration must be carefully adjusted. I have made nickel nitrate from the Dutch coin 'dubbeltje', which is made of 99+ nickel metal (with mainly tin as an impurity). I found that in HNO3 (60%) the nickel did not dissolve, in 40% HNO3 it dissolves vigorously, in 20% HNO3 it did not dissolve.

 

 

be careful :)

[Zoomboi]

Nickel does dissolve in nitric acid, but the concentration must be carefully adjusted. I have made nickel nitrate from the Dutch coin 'dubbeltje', which is made of 99+ nickel metal (with mainly tin as an impurity). I found that in HNO3 (60%) the nickel did not dissolve, in 40% HNO3 it dissolves vigorously, in 20% HNO3 it did not dissolve.

 

 

be careful :)

[Zoomboi]

I need to dissolve copper without dissolving the nickel. The coin is a Susan b Anthony dollar(nickel clad) and it has caked on copper corrosion from being stored with copper jewelry.

[OceanBreeze]

As a marine engineer, I know that pure copper is fairly reactive to salt water, while nickel is much less reactive. Most acids and alkalis will react with copper but not so much with nickel. Since you don’t want to damage the coin I would recommend a mild alkali, rather than an acid. Maybe toothpaste and a soft cloth will do the trick.  Another poster here, “exchemist” will have some better information for you, so you may want to wait until he comes along and answers.

Edited June 30, 2018 by OceanBreeze

[exchemist]

As a marine engineer, I know that pure copper is fairly reactive to salt water, while nickel is much less reactive. Most acids and alkalis will react with copper but not so much with nickel. Since you don’t want to damage the coin I would recommend a mild alkali, rather than an acid. Maybe toothpaste and a soft cloth will do the trick.  Another poster here, “exchemist” will have some better information for you, so you may want to wait until he comes along and answers.

Aha. Actually I was going to suggest a weak acid such as vinegar. The green is copper carbonate which should be removed by acids. Nickel will I think be fairly resistant. I see that vinegar or lemon juice with salt (as an abrasive) is a recommended way to clean copper utensils, so this gives me some confidence it should work. You may need to rub it to get the oxide layer off. 

[hazelm]

Aha. Actually I was going to suggest a weak acid such as vinegar. The green is copper carbonate which should be removed by acids. Nickel will I think be fairly resistant. I see that vinegar or lemon juice with salt (as an abrasive) is a recommended way to clean copper utensils, so this gives me some confidence it should work. You may need to rub it to get the oxide layer off. 

I know nothing of this but just wonder.  What about testing it on a common nickel that you don't mind damaging first?  See if it does any damage?  If that's doable, just use a Qtip and test a very small spot.  Then, if there is damage, it still passes as a nickel.

 

Just wondering. 

[Zoomboi]

I know nothing of this but just wonder. What about testing it on a common nickel that you don't mind damaging first? See if it does any damage? If that's doable, just use a Qtip and test a very small spot. Then, if there is damage, it still passes as a nickel.

 

Just wondering.

Thanks. I'll try that. I didn't realize that the Susan dollars and nickels had the same makeup.