Daniel

Topic: Asking about copper strike bath

Im dealing with a copper strike bath, i dont know the exact composition, i believe thet is not a rochelle type it is a plain cyanide type one.

I am surprised how difficult is to control the bath without a chemical analisis.  because the can be done each month, and the bath became unstable between thet period of time.

We proccess zamak parts, it is a zinc alloy, and the parts sometimes become qith a brassy appereance.

how can i know the reason of why is the bath attacking the zinc?

Maybe pH too high, if that is the reason how i can lower this value?

Maybe free cyanide too high?


it is best to change to a rochelle cyanide

Last edited by Daniel (12/01/2009 - 11:26 PM)

DustinGebhardt

Re: Asking about copper strike bath

You say that you are not able to analyze the bath, which will be helpful in trying to troubleshoot your problem. Do you know the pH? Typically a strike used over zinc parts has a pH around 9 or 10. A high pH will cause the substrate to be more-quickly attacked. You may be able to dummy out the zinc by plating at very low current densities, but this may or may not work for you. The Rochelle salts will help complex certain metals and improve efficiency, allowing higher current densities to be used. This may help you as the copper will preferentially deposit at the higher current density range and the salt may tie up some of the zinc.


But to prevent the zinc from getting into the bath in the first place, keep your pH low and make sure that there are no parts dissolving on the bottom of the tank.

-Dustin Gebhardt,
CEF
Plating Engineer
Danaher Tool Group
Gastonia, NC

Daniel

Re: Asking about copper strike bath

Thanks Dustin. How do you suggest that I lower the pH of the bath?

Paul Fisher

Re: Asking about copper strike bath

Hello Daniel Hope all is well for you during the holidays. I just wanted to drop by this discussion and remind everyone about a terrific article on this subject in the PF Online article archives written by Dr. Don Snyder of Ato-Tech Rockill, SC.

See below a sample chart from that article where he shows the typical makeup of the common cyanide based Cu baths..... including Strike, Rochelle, and High-efficiency. Check it out!

or click here to go directly to the full article.

Good luck and Happy Holidays!




Paul Fisher, Co-Host
Finishing Talk Live

Paul Fisher's Website

DustinGebhardt

Re: Asking about copper strike bath

Usually, a new cyanide bath has a pH close to 9.2 to 9.5. Usually, a rise in pH is due to an increase in carbonates and/or hydroxide.

What is your pH?

What is your carbonate concentration?

-Dustin Gebhardt,
CEF
Plating Engineer
Danaher Tool Group
Gastonia, NC