Electroplating Brass: A Mystery Unveiled

[mrjeffy321]

The other day I was at the store looking at some metal wall plates for light switches, they had all sorts of different types, Copper, Nickel, Stainless Steel, Chrome, …and “Brass plated stamped steel”.

How can it be possible to electroplate Brass onto something?
I understand how you can plate Copper or Tin or Silver, …., onto an object through the electrolysis of some solution containing those ions….but Brass?
Brass is not a pure metal; it is a mixture of Copper and Zinc. You cannot make a solution of Brass ions, only a solution of Copper and Zinc ions and then when you go to plate it out, shouldn’t it electroplate out as Copper metal and/or Zinc metal based on the Standard reduction potentials of the two elements?

The standard reduction potential of the Cu +2 ion to Copper metal is +.34 volts.
The standard reduction potential of Zn+2 ion to Zinc metal is -.76 volts.
These two values are a full 1.1 volts apart from each other, how can you plate them out together as Brass?

 

[mrjeffy321]

Could it be that "Brass" really isn't being plated on, instead, the company plates on Copper first, then zinc, then does something to mix the two layers together?

I got this idea from here,
http://sciencefix.com/lessons_matter_and_chemical_reactions.htm
they [galvanically] plate out some Zinc onto a Copper penny, then heat it to make Brass.

 

[Cesium]

I tried researching this and found several sources that said brass and some other alloys could be electroplated, but that others could not. I couldn't find any specifics on how the chemistry works. I think that there is a priority list that determines which metals go into solution first. I know that when I electrolyze an American nickel, an alloy of copper and nickel, that the nickel goes into solution first and I am left with a copper coin.