Nickel Sulfamate and Pits

Question:

We are having problems with pits in our nickel sulfamate plating line. What suggestions do you have to eliminate this problem? R.M.

Answer:

Your e-mail does not give me much to go on, but here are typical causes of pitting in nickel sulfamate plating baths.

Is there enough boric acid dissolved in the bath? Boric acid is not very soluble in a plating bath. Dropping of the bath temperature will cause boric acid to precipitate. It does not dissolve very readily when the plating tank is brought back up to operating temperature.

Is there enough antipitting agent in the bath? If the bath does not contain enough antipitting agent, bubbles tend to "stick" to the plated surface and pits are formed. You should monitor the level of antipitting agent by measuring the surface tension of the bath on a regular basis. The optimum surface tension for an air-agitated plating bath is 30-35 dynes/cm.

Do you have organic impurities in the bath? These usually can be removed by peroxide treatment followed by activated carbon filtration. Your chemical vendor can supply you with information on the proper procedure.