The authoritative public forum
  for Metal Finishing since 1989
  

  -----

BRONZE ELECTROFORMING

2000

Hi, I am interested in doing bronze electroforming.

1. Why can't I add bronze powder to a bath of distilled water and battery acid ⇦ this on eBay or Amazon [affil links] as is done with copper plating ?
2. Are there any incompatibilities with this mixture ?

The bronze powder is made up of copper and tin. There is no cyanide in the powder. I'm wondering why I've never seen bronze electroformed in any literature or postings. Any suggestions or recipes would be greatly appreciated. Thanks, Ed

Ed Cubberly
- Stanhope, New Jersey

---

Hey Ed, Industry doesn't use the sulphate bath (battery acid type)to plate Bronze. I'd find two references both Russian in the Chem. Abstr. 61, 1963 and Chem. Abstr. 70, 1968.

The tin in the alloy must be held between 8 and 15% for the deposit to be colored (red through yellow) tin at 20% is white. I think control of the tin content is the problem with the bath you want to use. Regards, Fred Mueller, CEF

Fred Mueller, CEF
- Royersford, Pennsylvania
2000

As you noted, and Fred confirmed, bronze is an alloy of tin and copper.

Now, since you mentioned battery acid, think about what makes a battery work. One of the metals wants to go into solution while the other wants to come out, and the tendency to do this is so strong that it will generate a useable voltage.

That's what you're fighting when you want to plate an alloy. Throw that bronze powder into the battery acid and what you will plate out will be more or less pure copper while the tin stays in solution.

What cyanide does for you is it complexes (ties up) the copper so securely that the amount of ionized copper available is infinitesimal and the balance shifts so that tin can plate out.

This is a hard topic to cover in a few short paragraphs, but if you look up 'Nernst equation' you'll see how it all fits together.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2000