How can I easily remove black from cupronickel after heating it?

[Letsurf]

So I'm using sparex no.2 to remove the black from silver after I heat it. I just quench in the sparex solution and it removes the black instantly. I'm trying to heat a quarter and use sparex to remove the black but it's not working. The quarter is cupronickel which is a mix of 75% copper, 25% nickel. Any idea what solution I could use to remove the black from the cupronickel after heating it?

 

[Bystander]

75% copper, 25% nickel

Not in Wiki's description of U. S. "sandwich" quarters. You've got two different alloys in a bath committing electrochemistry on each other.

 

[Letsurf]

So what is the solution?

 

[Bystander]

Depends on what you're trying to accomplish. If it's some sort of numismatic restoration, what is and is not acceptable is not something I know anything about.

 

[Nidum]

Citric acid - mild action .

Phosphoric acid based liquid soldering flux - medium action

Cold bath and soak in each case with agitation . Do not quench .

Several stronger solutions are available but probably not nescessary .

Citric acid is usually quite adequate for removing oxides from a one time heat of clean metal .

 

[Letsurf]

Citric acid - mild action .

Phosphoric acid based liquid soldering flux - medium action

Cold bath and soak in each case with agitation . Do not quench .

Several stronger solutions are available but probably not necessary .

Citric acid is usually quite adequate for removing oxides from a one time heat of clean metal .

Thanks for the tips. I heat, bend, reheat, bend the quarter to make rings. Is there something I can quench it in during this process so when I'm finished it will require minimum hand labor to polish? By the time I'm done shaping it now it is black from the heat and takes several minutes of intense hand polishing with steel wool to get the black off. With silver the sparex makes it a very simple process so I'm just looking for something I can use with the modern quarters that will make it easy.