Manage Current Density To Avoid “Treeing”

This column marks the end of my eighth year of attempting to give straightforward responses to day-to-day issues that arise in the electroplating arena. It is challenging at times but very enjoyable. All of the questions are real. Yes, I do edit if necessary and change people’s initials to help maintain anonymity.

I have learned that certain questions reappear on a regular basis and many problems and questions are easily answered in the format afforded by this column. Those that are not suitable for use in the column are usually handled via direct e-mail and/or phone discussions. Some questions are such that they can only be handled on a consulting basis. I will continue to respond to questions and problems in a timely manner and with information that can help solve your problems.

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Information sources

Question:

We are getting “treeing” and roughness on some of the parts that we plate in a Watts nickel plating bath. What causes this and how can we minimize the problem? I.W.

Answer:

Treeing or the formation of dendrites usually occurs when current density is too high or your plating solution contains insoluble particles. These same conditions can also cause roughness of the plated deposit.

To minimize this problem you should filter the solution thoroughly and if you are not already doing so, set up continuous filtration on your nickel tank. The continuous filtration system should allow for 2–5 turnovers per hour and the filter should have a 5–15 micron density. Vendors of filtration systems can be found in the Products Finishing Directory & Technology Guide under Filtration Equipment or by accessing www.pfonline.com/suppliers.html.

The second thing you should do is manage your current density better. If the treeing is found around the edges, more than likely your current density is too high. Try reducing the current density and see if this improves your results.