Zinc Plating and Crystal Growth

Q. We are running a potassium chloride zinc plating bath. The bath has heavy crystal formation throughout and a very thick layer of sludge at the bottom of the tank. As you might guess, we are not obtaining satisfactory plating from the bath. I have attached a few photos showing the tank and crystal growth. What is the cause of this, and how can we solve the problem? L. N.

A. I have received two e-mails in the past 30 days asking the same question. Both e-mails gave essentially the same information. One of these e-mails mentioned that they do not have any testing capabilities on site. The second e-mail containing photos is interesting because of the amount of crystals present. (My granddaughter did a crystal growing project last year and was really impressed with the photo.)

The sad fact in both of these cases is that the shops have allowed their plating baths to get completely out of control. Why? Neither shop has performed regular testing of the baths. I can’t offer much help in either of these cases because I don’t know the current “life signs” of the bath. The bottom line is this: You can not operate a modern plating shop without a testing program. Plating baths must be monitored on a regular scheduled basis. If you don’t have an in-house testing capability, then you must have your chemical vendor or an independent laboratory test your plating bath on a regular basis.