Q: We have six Watts nickel plating tanks, all of which are giving brittle, hard deposits. A typical analysis for these baths is:
|Nickel sulfate||170 g/L|
|Nickel chloride||89 g/L|
|Boric acid||47 g/L|
We have been able to partially solve this problem by diluting the baths 30% by volume. What can we do to solve it on a more permanent basis? K.Y.
A: The data you have supplied indicates that the concentrations of nickel sulfate, nickel chloride and boric acid are in the correct range. (Note: for you chemists out there I have assumed that the nickel salt concentrations are not reported as nickel sulfate hexahydrate and nickel chloride hexahydrate.) The values for the “tramp” metals are also reasonable except for iron, which is a little on the high side. Dummying of the baths should be done on a more frequent basis.
Your e-mail does not mention whether your plating bath is a standard Watts bath or a Watts bath with organic additives. If you are using an anti-pitting agent in your baths, you have an organic material present. Most organic additives, whether simple anti-pitting agents or brightener systems, break down in use. Where do these decomposed organic materials end up? Not in the atmosphere, but in the plating bath itself! These decomposition products cause hardness and brittleness in the nickel deposit. Whatto do? The old standbyactivated carbon treatment is the answer. In the old days, treatment with activated carbon was always considered a nuisance but today there are easier-to -use carbon treatment methods. Contact a vendor that specializes in filtration equipment for help solving your problem. You can find companies by going to www.pfonline.com and searching the vendor database under “Plating Equipment”.