Metal finishing Q&As since 1989

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Reducing sulfur content of nickel deposits

2003

Hi,

I'm about to finish my Master's degree in electrochemistry at Queen's University, Canada. I'm working now on a project in a way to electrodeposit a thick (about 2mm) Ni layer. I think that the best choice would be sulfamate since I need a very thick layer, but I am also required to obtain a very pure deposit, so I am wondering about the addition of sulfur in the deposit related to the utilisation of nickel sulfamate. So my question is if there is somebody who know a good procedure to minimize (or avoid) the amount of sulfur in the nickel deposit, or if there is some ways to obtain such a thick layer with other baths.

Thank you.

Sylvain Bolduc
student in electrochemistry - Kingston, Ontario, Canada

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Hi Sylvain

Personally I haven't a clue as how to help you .,...but you could try the world's most informative nickel suppliers/producers.

That's SPECIALTY METALS in the USA or SPECIALTY METALS WIGGIN in the UK ...but Wiggin at least replies to inquiries whereas the U.S. Company doesn't always do this.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
2003

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My first question is how pure is "very pure"? Obviously sulphamate contains sulfur, but the sulfur deposited in electroformed nickel usually comes from other additives such as saccharin, wetting agents, stress relievers, etc. Saccharin is used as both a stress reliever, hardener and leveler/brightener. I believe that the most common source of sulfur in nickel deposits is the saccharin. Even so, the levels are extremely low, typically being 0.05% or less. It is well known that sulfur can have a detrimental effect on the brittleness of electroformed nickel, especially if it is heated to over 160C. To overcome this problem, yet maintain at least some of the characteristics of a saccharin bath, you can use cobalt as a hardener. Your problem then becomes one of obtaining a low stress deposit that has all your other requirements. To achieve a coherent electroform, 2mm thick material must require a low stress deposit or it runs the risk of fracturing. If you can tolerate extremely low levels of possible sulfur, sulphamate will not cause you a problem as long as there is no other sulfur containing material in the bath. You must then seek wetting agents and other additives that do not contain sulfur. I suggest you talk to your supply house or do an extensive literature search. There is also one other issue; most electroformers use sulfur depolarised nickel as anodes; this is to assist the dissolution of the anode, so this too may be a potential source of sulfur. One way around that is to use sulfur free anodes, but you will need to add chloride to the bath to promote anode dissolution. Chloride will also induce stress, so you will need some stress relievers.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003