Removing sodium ion form nickel solution

A. I have never heard of a way to remove sodium ions from a nickel bath.
You took the cheap way of adding chloride and now you pay the price. Two possibilities-dump the tank or dump half of it and get by for a few years.
There is no reason to ever have to raise the pH except adding too much acid and possibly-using inert anodes.
Why do you think that the high sodium content is causing the salt spray failure?

A. Perhaps I am missing something, but why is the presence of sodium ions causing salt spray failure? Salt spray failure is due to a breakdown of the surface coating - be it a conversion coating or a metal deposit. It sounds like the nickel thickness is wrong, so increase the amount being deposited.

Sodium salts and ions are, as far as I know, impossible to remove from a working nickel bath.

They will affect the conductivity of the electrolyte and it is claimed it affects the stress in the nickel deposit, although I have never seen it. It is also supposed to adversely affect the throwing power, but only to a minimal extent. The high alkalinity that can be generated by adding excess sodium hydroxide can result in porosity and roughness caused by insoluble hydroxides, but this can be overcome by running the bath at a lower pH.

I strongly recommend you improve your general housekeeping - a well kept and well run plating facility would never let this situation occur - I suggest spend some time sorting your shop out.

Carry out a Hull Cell test to see exactly what damage you have caused and then re-assess your plating options- it may not be as bad as you think, but please get your workshop tidied up!

A. Dear Aboo backar,
Cutting the bath is the best option.
In future do not add sodium hydroxide directly in to the bath even for increasing the pH.Best way is to make a slurry of sodium hydroxide with the nickel bath solution; say 500 grms of NaOH+10 ltrs of Nickel bath solution in a 20 ltrs bucket.Lot of heat will be evolved.So take care.Let it become slurry in 5 minutes.Stirr well carefully.Add water to the brim.leave it for 1 hour.throw away the supernatant clear water which will have excess NaOH which will harm the plating bath.repeat this exercise one more time.Then You will get purr nickel hydroxide and can be used to increase pH with out the fear of contaminating your bath with sodium ion!
Take care, Good luck.

Q. Hello,

Thank you Ted for your reply. I did not know that Na could cause problem in nickel plating, I will investigate in this topic.
About NaCl, I learned that some baths which we call "USA Nickel" ou "American Nickel" are made with NaCl, NiSO4 and H3BO3. But you are right, the most nickel baths are made from the traditional Watts Nickel (NiCl2, NiSO4 ant H3BO3). If somebody use a USA nickel, let me know why this bath is done with NaCl?

My objective is made a nickel bath as a layer under a precious metal. I think a Watts nickel could be used (with additives if necessary).

Best Regards

A. NaCl will supply adequate chloride, BUT...

All that Na will cause a brittle deposit

A. Here, page 70. https://www.nmfrc.org/pdf/psf2002/090268.pdf

Note, small quantities of Na from addition agents, etc are okay, but using NaCl to replace Nickel chloride will embrittle the deposit.

A. My preference would always be for NiCl2, because NaCl is much less soluble and Na ions can cause stress in the nickel deposit. The reason for adding chloride ions to a Watts nickel bath is to promote anode dissolution, unless you are using sulfur depolarised anodes when, in theory, you do not need chloride ions; this is one of the advantages of nickel sulphamate baths.