Which metal deposits first: Cu or Ni?

[floydnfish]

So, I'm trying to electrodeposit Cu-Ni alloy. Cu being more nobel than Ni as seen from the EMF series. My simple question is that which of the two will have more tendency to electro deposit first. And, how can I control the amount of Cu-Ni composition in my deposits. I have a common bath of electrolyte containing both Cu-Ni ions.

Thanks, will be waiting for a response.

 

[Baluncore]

Welcome to PF. Sorry about the delay.

Write out the half cell equations and work out the potential required to deposit Cu or Ni.
What are those voltages and how different are they ?

The cell voltage will need to be sufficient to deposit both elements.
An alloy will be difficult to deposit unless you carefully control the concentration of the electrolyte.

 

[floydnfish]

Thanks for your reply Baluncore.

So the reduction potential for Cu is 0.34, and that for Ni is -0.25.
I'm keeping my cell voltage at 5V for my experiments. And the electrolyte concentration anywhere from excess of Ni sulphate, some amount of Cu sulphate and Na citrate less than the total Cu+Ni amount. These are the kind of electrolyte concentration popular in the literature. But, I've failed to deposit considerable amount of Cu-Ni alloy with the above mentioned voltage and electrolyte recipe. I'm trying to deposit pillar structures, but all I get is a minor small spot and some amount of electroplating involved. It'd be a great leap for me to be able to figure out the right electrolytic concentration and get a pillar deposit. It would be good if you can suggest me more. Thanks.

 

[Baluncore]

These are the kind of electrolyte concentration popular in the literature.

Can you give me a list of references to your relevant literature. Which references describe Cu-Ni alloy pillars?

Can you say why you want Cu-Ni pillars? What dimension pillars do you need? What is the deposition substrate? Do you have references from literature that give current density, electrode geometry and the dimensions needed?

Have you seen this open access paper on "Electrodeposition of Cu–Ni Composite Coatings". It is chapter 5 of "Electrodeposition of Composite Materials", 2016, Edited by Adel M. A. Mohamed and Teresa D. Golden.
https://www.intechopen.com/books/el...electrodeposition-of-cu-ni-composite-coatings