Metal finishing Q&As since 1989

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Nodules in Nickel Plating

 

I am currently experiencing a nodule problem with our Nickel plating process - Watts type formulation. Chemical balances are in order with appropriate filtration, electrolytic purification and Carbon treating. pH is maintained @ 3.8. I am convinced it it not a particulate contamination problem being dragged into the bath. Chemical analysis has revealed no detectable limits for Cu, Fe, Mg, P, and Zn. However, there are 150 mg/l of Ca and 4900 mg/l of Na. We currently soften the water used for make up lost due to evaporation. Has anyone else experienced a similar situation.

Stanley A. Watson
- Marlborough, Massachusetts

May I know temperature used? Have you checked contaminations of Chrome? Do you have a hole in anode cloth/bag? What current density are you using? How is hull cell? What is chloride level used by you? Do you see Nickel particles in bath at ends?

Payal Mag
- Charlotte, North Carolina
 

Bath temperature is 155 F, there is no Cr present, the anode bags are double (two separate bags over one another). The current density is 55ASF and the Hull cell test looks great, bright finish over the entire current density range. The bath is a high chloride concentration in the 15 oz/gal range.

Stanley A. Watson
- Marlborough, Massachusetts
 

With data given, it looks like leak in filtration. You can take bath solution in Lab and filter using 0.45 micron filters under vacuum. Observe particles on paper.

Payal Mag
- Charlotte
 

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It could well be that your problem is calcium contamination. Calcium (as calcium sulphate) has a reverse solubility, that is, it is less soluble at high temperatures than at low temperatures. Calcium generally precipitates from the solution as needles but, depending on the operating conditions, can also precipitate as granules. The concentration quoted, 150 mg/L is close to the solubility point at 155F. If at all possible, lower the temperature to 140-145F and see if the problem goes away. If it does then it will be necessary to remove the calcium by batch treatment in a separate tank. The best material to use is sodium bifluoride. It must be added in amounts less than the stoichiometric amount. An excess of fluoride is dangerous and may result in the attack of titanium anode baskes, if used. The fluoride treatment also removes magnesium. Therefore, it will be necessary to analyze the solution for both Ca and Mg just prior to the treatment. The plating tank must be thoroughly cleansed since there may be residual Ca salts on the tank walls and anodes.

Lou Gianelos
Retired - Eastlake, Ohio
 

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Calcium will causes small pimples but not really "nodules". Low pH favors noduling, so raise the pH to about 4.1 or maybe 4.2. Squiring agitation causes nodules, so be sure the agitation is a moderate movement and not squiring on the spot that is noduling. As stated in all of the above, any contamination contributes to noduling, pH and agitation just exagerate the formation.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

 

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Q. Hello

I plate nickel and chrome on steel (musical instrument). But after nickel plating, I can see many small nodules on the component. My process is soak clean + Electroclean (alkaline)+ Acid dip (Acid salt) + Watts nickel (with GL-1 additivefrom ATOTECH) + Bright Nickel + Chrome.

I don't know that the process mentioned is sufficient or not. Someone told me that I have to increase Acid Electroclean (-) and Alkaline Electroclean (+) to prevent nodules after Bright nickel especially for steel. Is it true?

Thank you

Aon Dum
- Bangkok, Thailand
May 16, 2012

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