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Nickel anodes turning black
We received a new batch of nickel anodes from our supplier and they are turning black in our strip plating bath. The supplier said that the only thing that would make them turn black is if they contain sulfur and we have not been able to find any sulfur. The other odd thing is that we have tested both the new anodes and the old anodes to determine if there are any differences and we have not found any. Any help you can give us on this matter would be greatly appreciated.
Littelfuse - Des Plaines, IL, USA
All sulfurized anodes turn black with inorganic sulfur matter. The blackness forms faster at lower pH,higher halogen content, higher anode current density, and as a function of the sulfur contained. That is why we use anode bags. Tell us what kind of nickel anodes you are using, the electrolyte, the pH,the halogen.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
There is insufficient information to make a judged comment, but I would suggest two things. Firstly the nickel contains sulphur and the blackness is due to that. The usual amount of sulphur in sulphur depolarised nickel (aka S nickel) is well below 1% ( I believe it is as low as 0.2% but I would seek a second opinion on that!); they are usually supplied as rounds. If the nickel is not as rounds, it may well not be "S nickel". Alternatively, the nickel has passivated and the blackness is the nickel oxide. A lot more information is needed, such as what are the bath composition and operating conditions. With this information, perhaps a more helpful comment can be made.
R&D practical scientist
Chesham, Bucks, UK
I also agree that the information is a little insufficient, but we have this problem also, in our Ni plating bath. We use 60 inch titanium anode baskets then have them covered with triple flocked bags to keep the fines out of the bath. Anyway,we always use electrolytic "R" rounds for our bath and we got sent "S" rounds by mistake,we did use them but all the "S" rounds have turned black and all the "R" rounds are still the grey color they normally are. We run a ph of 2.00 and the temp is 140 degrees.Brian Gaylets
- Scranton, Pennsylvania, U.S.A.