Pitted Copper

Q: We use a copper sulfate plating bath. We recently have been observing pitting in the copper deposits. Addition of brighteners seem to improve our results but only last for a short period of time. Our chloride concentration is about 115 ppm. I should add that we have operated at higher chloride concentrations in the past without any problems. Do you have any suggestions for solving this problem? D.W.

 

A: There are a number of possible causes for the pitting that you are observing. The first thing I would do is look at the makeup of the plating bath itself.

I would start with the brightener system. It is very possible you have a high concentration of what I call “organic trash” which can build up over time as some of the brighteners decompose. I would suggest a carbon treatment of the plating bath as the first step.

The next step would be a complete analysis of the components in the bath. If you are unable to perform this analysis, the vendor of your brightener system should be able to help you.

While you state you have operated in the past at higher chloride concentrations, I would reduce the concentration in the bath.
Look at your filtration setup. Maybe you are really not filtering your plating solution because of leakage in the system. You may be having a problem with air being sucked into the system by the filtering system.

Check out your anodes. Are you bagging the anodes? Perhaps some of the bags are perforated allowing metallic materials to be suspended in the bath.