Letter 10897

Copper on titanium electroplating 

Can someone help me with a copper plating problem?

I'm trying to plate copper on a titanium electrode in a solution of CuSO4, H2SO4 and a little HCl. The problem is that a very dark red(almost brown) very porous copper layer is formed on the titanium cathode. It is easily washed away with water after taking it out of the plating bath. It also seems like reaction tends to stop after a while, the current decreases when a constant voltage is used. When pH is low there is gas formation at the cathode, H2 I guess. What can I do to get solid bright copper?

Is it at all possible to plate copper on a titanium electrode?

Do I have to change the electrolyte composition or use any additives?

My composition is:

[Cu] 300mM = 75g/litre
[H2SO4] 90ml/litre (95% H2SO4, pH<0)
[HCl] 0,16ml/litre

Patrik Moller
- Lund, Sweden

Hi Patrik,

The first thing you have a very bad adhession for the copper to titanium, is difficult to plate on titanium. I have some different pretreatments methode to do this activation. When the current decrease is the same as your anodes is passive no current will go through the anodes. I think you can see a black film on your anodes. About your pretreatment you must explaine more about how you did your pretreatment step before the copper plating. To get a more brigther copper deposit you can try this methode. 50 gr/l Coppersulphate, 180 gr/l kalium natriumtartrat ( Rohellsalt ), 50 gr/l Sodiumhydroxide.

Regards,

Anders Sundman     surface finishing engineer Sweden

Patrick,

Are you following the stict steps of activation in 3:1 HNO3-HF to red fuming and the dicromate? Are you controlling the HF content closely?. Your acid copper doesn't seem to be the problem. Please give us more info to better help.

Regards,

Guillermo Marrufo
Monterrey, NL, Mexico

Thank you very much for your advise.

As pretreatment I've been using this cleaning process for both titanium cathode and copper anode:

1. Thorough washing in detergent solution
2. NaOH 10%
3. H2SO4/HCl 10%
Rinsing after each step.

After your replies I've also been trying the activation process with 1:3 HNO3:HF solution. There was a reaction taking place with gas formation(green). It was obvoius that the solution etch the outer layer of the titanium electrode, it was smaller afterwards. Is the purpose to remove a TiO2 layer?

Unfortunately the plating wasn't much more successful afterwards. I still get the very porous dark copper that falls apart. It seems like there is a thin bright copper layer right next to the cathode, but when running the process for a longer time it is also converted into this porous material. Two times I've succeeded getting a thin bright deposit, but only when running the plating for a short while.

I have the option of depositing another metal layer on top of the electrode and now I'm thinking of what metal to use. Platinum or palladium should be good I guess, I want it to be a good copper seed material and at the same time very inert in the electrolyte. Another option may be to make the whole electrode in stainless steel. What materials are the best when it comes to copper seed properties?

One last question, what current density range should be used for a bright solid deposit according to you?

Best regards,

Patrik Moller
- Lund, Sweden

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