Consumption of nickel anodes

A. Mr. Gomaa,

Unless something is very unusual with your nickel plating process, all of the nickel that dissolves from the anodes goes onto the parts. So you need to approach it from the other direction, i.e., you have to decide how thick the nickel plating must be. Then however much nickel you plate is how much nickel anode you will consume.

A. Theft

A. Hi,

I'm with Ted on this one. The rate of anode dissolution is determined by Faraday's law, same as the rate of nickel plating. Anode current efficiency can be calculated the same as cathode current efficiency (actual weight dissolved/weight predicted by Faraday's law).

The pH, etc. has very little to do with the rate of anode dissolution. The corrosion of nickel in an anode basket is electrolytic, not chemical. One caveat to all of this: If, for some reason, your nickel is not corroding properly, you may be generating large amounts of anode residue, rather than having the nickel dissolve. Then you would need clean your basket more often and add more nickel squares, or whatever form you are using.

A. As I understand your problem, you are dissolving more nickel from the anodes than you are depositing onto the cathodes. As everyone above has said, nickel dissolution and deposition follows Faraday's Laws and both sides of the chemical reaction are pretty close to 100% efficient. If we assume your bath composition is basically in specification, then it must mean that your anode and cathodes are electrochemically out of balance. If that is not the case, then you must be depositing nickel onto something other than your workpieces. Have you checked for any unwanted nickel deposits in the tank caused by stray currents - if you have any, this will affect the apparent efficiency of your process tanks, because you will be applying a lower cathodic current density to what you were aiming for. Consequently, you will be taking out less nickel from the tank than you originally thought (and calculated for) and so when you calculate what you are actually taking out and what you are actually putting in, there will be a difference. Similarly, if you are only partially dissolving the nickel and getting lots of sludge in your anode bags, you will be losing more nickel from the anode than you are putting down on the cathode. However, if the concentration of nickel ions in solution is increasing, then you must be either dissolving the nickel anodes chemically, which is most unlikely if the electrolyte is in specification, or you have a stray electric circuit with a cathode that does not let the cations deposit onto it. Finally, are you sampling your bath at the correct tank volume - if there is a lot of water evaporation, which in Egypt I would suspect there is, you must make sure your tanks are kept at the correct volume or you will get misleading concentrations for all components of the electrolyte(except water!).

Very good answer, Trevor. Thanks!

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Dear Aly,

What is the concentration of chloride ions in your bath check it. If you want to know with out analysis. Check the stress of your deposition if it high chloride is too high.

A. Dear Sir,

Hi I think maybe you have a problem in your bath which leads to passivation of articles at cathode during plating. For ex. in case you have more brightener or overdosing in the bath the cathode will become passive very fast. So instead of nickel deposition the Hydrogen will involve at cathode so anode dissolves correctly but the deposition of nickel ion at cathode is not according Faraday law. please check the sign of passivity on nickel for ex. the chrome deposition, white stain,.. The other possibility can be stray current in the bath. if you have stray current in bath maybe instead of nickel deposition on some metallic device ( heater, heating coils,..) the hydrogen gas forms.

A. Yes, the nickel will dissolve in the acid portion of the solution. You should notice a rise in the pH.
Remove the anodes when not in use. I like to store them in a plastic drum of water with a few drops of whatever acid you use in the tank. This will keep them from oxidizing or going passive.
For the tank solution, I would decant whatever % it is in excess and store it for required additions or eventually a new makeup. The decanted tank then needs to have the necessary amount of water wetting agent and acid to bring the tank up to normal.
You could use insoluble anodes for plating out of the high nickel tank, but this will affect internal stress and the pH.

A. Hi Bojan ,

Yes Yes Nickel anode dissolves, if there is no electric current running through the cell.

Approximately one gram of nickel anode is dissolve in one litre of nickel (at ambient temperature, pH - 4.5 to 4.9) plating solution in one day.

Remove the nickel anodes when not in use or while the concentration of nickel content is maximum in the bath.

Regards,

A. Hi Thomas. I would start by simply reducing the number of anode baskets slightly. We put your inquiry on this thread, where you posted it, because you refer to this thread's other comments, but thread 7124 addresses nickel concentration rise more directly, as you probably know because you've discussed it on that one previously. Good luck.

Regards,

A. Nickel anodes dissolve at 98-100% Faraday efficiency but plate out at only 95-97% efficiency. This discrepancy can lead to nickel growth in the plating tank if not reduced by dragout or decanting.

A. Hi plating people.

A high or rise in nickel concentration is from chloride and sulfuric. But it come from the the nickel if it does not have 100 percent plating efficiency, that is if it only has 80-90 percent.

Best regards,
4 generation plating engineering
Sweden