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Our problem is skip plating in nickel

We can not plate in our nickel tank. we are sure that no chrome contamination went into the tank. We have got this problem as we added carbonate nickel to tank for increasing ph. At the moment after we decrease ph with adding 1 cc of H2so4 to solution the problem is gone and we can plating. but if we increase the ph to desired value for satin nickel we have got that problem again . can you give me any recommendation ?

thanks,

Saeed Ghasemzadeh
- Tehran, Iran
2007

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Saeed,
The instant Ni carbonate must be fully dissolved in the plating solution before you begin plating or you will have problems. I always preferred a ph of 3.8 for Ni sulphate baths (assuming you have this type). What is the desired ph for your "satin" finish? Are you using a wetting agent in the bath?

Mark Baker
Process Engineer - Syracuse, New York
2007

Dear Mark Thank you for your reply.I think we did not dissolve carbonate in plating very well and also I think our carbonate has a lot of sodium carbonate . Our desair ph is 4-4.2 for satin nickel.If you have any recommendation for solving this problem please write for me.

Saeed Ghasemzadeh
- Iran
2007

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Saeed, firstly, you do not give any formulations for your bath. Make sure you have adequate wetting agent and boric acid in the bath. I notice you only need to add 1cc of sulfuric acid to the bath to get the correct pH, but this is a very small amount of acid to add to most baths, unless it is a very small bath volume! This makes me think the bath is not adequately buffered. Secondly, I presume you are using a sulphate bath since you add sulfuric acid; the optimum pH for this type of bath would be 3.4-3.8, but you want 4.0-4.2; however, you know your bath better than anyone else!. Finally, make sure all your nickel carbonate is dissolved and the bath is at the correct pH. I would not expect any nickel bath to require constant pH adjustment unless there is something wrong with either the formulation (no buffering) or the anodes are passive and are discharging hydrogen.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2007