Does agitation effect the deposition rate in Electrodeposition of Copper?

Raghavender Reddy Jakka @Raghavender_Reddy_Jakka

07 July 2016 9 2K Report

I tried electrodeposition twice by varying the speed of magnetic stirrer, mechanical agitation.

The parameters I used are as follows:

Electrolyte:

150mL DI Water

30gms Copper sulfate

5mL sulfuric acid

Electrodes:

Anode: 37mm x 28mm x 0.76mm Copper-Phosphor

Cathode: 28mm x 22mm Pure Copper

Surface preparation:

Cathode was polished to 0.1 microns

Anode was ground till 1200 grit paper

Then both electrodes are ultrasonically cleaned, placed in acid dip solution for 45secs and rinsed with DI water.

Other parameters:

Current: 0.2A (constant)

Magnetic stirrer: 200rpm & 1000rpm

After 3 hours of electrodeposition, with 200rpm, the voltage started fluctuating between 0.47 and 0.42V. Upon inspection, I found blue crystals on the anode. Then I replaced anode with a fresh one of the same area. This time, the voltage fluctuation started after 5 hours, same blue color crystals on the anode. I removed cathode, there was uniform copper deposition of around 400 microns.

I thought the agitation was the problem and tried 1000rpm this time, keeping other parameters the same. The voltage fluctuation started after 5 hours. Same blue crystals and had to replace the anode. To check whether stagnation of sulfate ions is causing the problem, I placed an Aerofoil kind of thing on the edge where the vortex, which is caused by the stirring, meets the anode. I inspected the anode after 3 hours and found some crystals on the anode. The cathode had uniform copper deposition, but only around 200 microns in thickness.

I increased agitation to prevent the formation of crystals on the anode. As a result, the crystals density on the anode reduced at the expense of deposition rate.

I have attached a picture of the anodes after electrodeposition.

My question are

Does agitation effect the deposition rate?

Is crystal formation on the anode, an indication of insufficient agitation?

Cornel Radu

Do you have considered 30 g of CuSO4 or 30 g of CuSO4.5H2O?

Do you have significant evaporation/loss of the solution after 5 hours?

Looks like the solution becomes saturated. Reduce the initial concentration of copper sulphate.

Stirring is not the best idea...a uniform flow is better. In any case reduce the stirring rate (200 rpm or bellow). .

Raghavender Reddy Jakka

Hello Cornel Radu,

Thanks for your reply.

I am using anhydrous copper sulfate. So, its 30gms of CuSO4.

No, The evaporation is negligible because I don't see any significant drop in the solution level.

Do you think the copper ions in the solution increased as the anode area is way more than that of the cathode, which saturated the solution as the time passed?

I read in metal coatings handbook that the electrodeposition of copper in sulfate bath requires vigorous agitation. That's the reason I am using mechanical agitation. By uniform flow, do you want me to recirculate the electrolyte by using a pump?

Cornel Radu

The concentration of CuSO4 is too high. The solution is saturated (consider also the presence of common ion SO42- from sulfuric acid). Reduce it to half.

The anion SO42- migrates to anode where you also have supplementary amount of Cu2+ from dissolution.

What do you want to do? Cu refining or Cu recovery from solution?

Raghavender Reddy Jakka

I think 31 grams of anhydrous copper sulfate is the saturation point for 150mL water.

Do you want me to reduce the the copper sulfate to 15gms?

I need a uniform deposition of copper on copper substrate.

Cornel Radu

Read here

https://en.wikipedia.org/wiki/Solubility_table

and consider also the presence of sulfuric acid. The solubility is much lower.

Raghavender Reddy Jakka

Thanks for the link.

Can you please take a look at this link?

http://www.inchem.org/documents/icsc/icsc/eics0751.htm

This website mentioned the solubility of anhydrous copper sulfate.

Raghavender Reddy Jakka

No, sir. I just need uniform Copper deposition on the cathode, that's it. Today I tried 1:1 for cathode and anode area with 200rpm agitation with an electrolyte containing 27gms CuSO4, 4mL H2SO4, and 150mL DI water. This time crystals formation started after 3hours.

Hamidouche Mohamed

what is the applied current density ? it is indesponsable to mention its value and also the bath temperature. so that we can help you

Moreover, you want to elaborate Cu electrodeposits , so the anod should be Cu not Cu-P

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