The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Plating an alloy

I have a need to know whether the electrochemistry of plating an alloy is different than plating single metals, specifically whether both metals will still plate at their same standard reduction potential. For example, if I wanted to plate an alloy of platinum and lead (reduction potentials +1.118 and -0.126 vs. standard hydrogen electrode respectively) would any of the lead plate out at a potential more positive than -0.126? That is, are there some voltages that the platinum would plate by itself and leave the lead behind or would the platinum always carry at least some of the lead along with it when it came out of solution?

Matt Chambers
Researcher - Goleta, California
December 7, 2009

Hi, Matt. For quantitative data look into the Nernst Equation, which takes concentration as well as standard reduction potentials into account. But the short answer is that the platinum would plate by itself in your case.

To plate alloy coatings it is generally necessary to complex the metal which has the more positive reduction potential to"tie up" those ions and give the other metal a chance to deposit.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 7, 2009

---

Q. Looking at old books concerning the manufacture of "Imitation Alloys", does anyone know if the alloys can be electrodeposited on steel. My interest is in the making of Imitation Platinum in ingot form and then using the platinum in coating a piece of steel.

How would I go about this?

Dwayne Weber
- Chicago, Illinois
January 20, 2012

---

Hi, Dwayne. Almost nothing is totally impossible, but many ideas present barriers so formidable as to be discouraging.

The reason that batteries work is because different metals can have radically different electrochemical potentials. To simultaneously plate two metals is therefore difficult and requires special chemistry; there are only a couple of tri-metal alloys that have been successfully plated (white bronze probably being the most common). If you can tell us the composition of the alloy in question people may be able to advise whether they think you have a fighting chance; but if you do, it will require specialized chemistry, not plating out of simple metallic salts. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January , 2012