Should We Use Educators to Agitate our Plating Baths

Q: We are looking for a better way to agitate our plating baths. Currently we are using air agitation but one of our vendors has suggested using eductors. Should we and if so, why? S. W.

A: The short answer to your question is an unequivocal yes. I addressed this question in one of my earlier columns. Here is what I wrote at that time.

The classic way to agitate plating solutions has been either air agitation or, to a lesser extent, cathode reciprocation. A paper, Exploitation of Eductors Agitation in Copper Electroplating, D. R. Gabe, M. Ward and J.N. Crosby, presented at the June 1999 Sur/Fin, American Electroplaters & Surface Finishers Society, www.aesf.org, addresses these questions. Using a mathematical relationship which we needn’t concern ourselves with here, the following enhancement factors were
determined.

Agitation Method	Enhancement Factor
Static solution	1
Natural convection	1 – 2
Cathode reciprocation	2 - 4
Air agitation	2 - 5
Vibratory	3 - 30
Turbulent flow	5 - 15
Ultrasonics	2 - 10

As can be seen from the above data the agitation method used does make a difference. Surprisingly, the two standard methods, cathode reciprocation and air agitation give similar enhancement factors. The data above also indicates that the vibratory and turbulent flow methods of agitation offer real improvements over the two classic methods. The vibratory method is usually not used in the plating industry; however, the turbulent flow method is used.

The use of eductors will give you a turbulent flow environment and based on the information in the table much better mixing compared to cathode reciprocation or air agitation. An eductor is a specially designed nozzle that causes liquid pumped through the nozzle to exit at high velocity. This in turns pulls additional solution from the surrounding region through the nozzle.

Yes, I recommend eductor based agitation systems. More information on the process and vendors who sell the eductor nozzles can be found at the PRODUCTS FINISHING web site, www.pfonline.com.