Crystals in my Plating Tank, Part II

In my September 2004 column, I answered a question regarding crystals in a Watts nickel bath. One of our readers was kind enough to send some additional information to me about this phenomenon. For the original question.

Additional Information:

The quality of the boric acid also makes a difference. In this particular case a plating shop had a 2,400-gal Watts nickel bath that was not used during the weekend. The air lines used for agitation of the bath plugged up over the weekend and large crystals formed in the plating bath. In addition, staining would occasional occur after the nickel-plated parts were plated in a tri-chrome bath. This crystallization had not been observed earlier. The boric acid was immediately suspected, but why all of a sudden did greater amounts of crystals form? Turns out the supplier of the boric acid had changed its vendor a short time prior to this problem appearing.

To test whether the boric acid was the culprit, two Watts bath, were made up: one using the previous brand of boric acid and one using the new brand of boric acid. Identical sized samples were taken from each bath and allowed to cool overnight. The sample with the original brand of boric acid contained approximately 30 cc of precipitate while the sample containing the replacement brand of boric acid contained approximately 160 cc of precipitate.

The plating shop went back to using the original brand of boric acid and the plugging of air lines and the staining disappeared.

The bottom line: The quality of chemicals used in your plating baths can and do make a difference.