My nickel bath has crystals, what can I do to liquefy of them?
Q. I work in a small PCB house and we have a nickel bath to plate edge connectors. Sometimes it gets a lot of use and other times it just sits idle. We have a problem with crystal formation which occupies quite a bit of our bath. We would like to "de-crystallize" the nickel and continue to use it, is this possible? What techniques can we use to liquefy these nickel crystals and incorporate the nickel back into our plating process?Cliff Heckenberg
A. Recrystallization comes from loss of water and consequent cooling. Add the required amount of water to restore original level, a little heat and patience. No big deal. Then analyze chemistry.Guillermo Marrufo
Monterrey, NL, Mexico
A. The crystals are probably boric acid, if I had to guess. When you aren't using the tank are you letting it cool down? My nickel tanks run boric acid at close to the solubility limit so the boric can crystalize out at lower temps. You will probably cause roughness if you add them directly to the tank. Put the crystals in an anode bag and drape the bag over the side of the tank when it is at temperature.
A. By "liquify" I presume you mean dissolve. I also assume the bath only shows these crystals when it has been idle and allowed to go cold. The best thing to do is to make the bath up to its correct volume (specification) and then turn on the heaters. If there are a lot of crystals around the heater, you may want to turn the pumps on first and allow them to start to dissolve, otherwise you may burn them out. Analyse the bath to make sure its in spec before you use it.
R&D practical scientist
Chesham, Bucks, UK
A. Probably what you've got is boric acid precipitating out; many nickel baths run with the boric acid concentration close to saturation. As a rule, heating the bath with agitation will redissolve the crystals. I used to run into this with a tab plater; the crystals would plug the sparger holes in the plating cell.
- Tallahassee, Florida
A. What kind of nickel plating solution is it? Is it Sulfamate?
If sulfamate and it has been heated or run at too high anode current density then you have broken down the SN radical into ammonia and sulfate. Go get an ammonia analysis because you may have to dump the bath. Let us know the ammonia content.
If it is simply Boric Acid in a sulfamate bath, you must know that the solubility is limited by the operating temperature. If it does not dissolve at your operating temperature, then you have too much, get it out, filter it out.
The old timers used to say to hang a bag of boric acid in the corner of the tank. That is OK for a sulfate solution. That is not OK for a sulfamate solution. Over the weekend it cools and falls out. On Monday morning the lab tech titrates and adds more boric acid but it will not go in.
Come back with some more information.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
and co-author of The Sulfamate Nickel How-To Guide
August 5, 2018
Q. Hi! We are running Ni baths using Ni sulfate solution; and white precipitate forms above the anodes and anode basket readily than those baths using Ni sulfamate. Is this really normal? How do we minimize or eliminate the formation of precipitate? Our preventive countermeasure is to check the baths every day and remove the precipitate manuallyKim Bernat
- Laguna, Philippines
A. Hi Kim. Yes, this is almost surely boric acid. Please double check what concentration you are trying to hold, and the temperature of the bath. You asked the same question two weeks ago as topic 11706 and Robert Probert answered it the same way. Good luck.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"
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