-----

Cobalt plating on Copper surface

I would like to do pure Cobalt plating on a copper lead frame. Would your please suggest me the what solution and the process that are required. Also, are there any safety issue? Thank you for your help!

Benjamin Chan
HKUST - Hong Kong
2000

Hi, Benjamin,

You could dissolve cobalt chloride or sulphate into water, and adjust the pH with acid, add wetting agent, levelers and brighteners, and make a plating bath. The chemistry is really just about the same as nickel plating.

But most industrial plating is done from proprietary plating baths, rather than being brewed from raw materials by the users. So you will probably not easily find enough info here or in books to formulate your own solution that is really the equal of commercially available processes; rather, you should buy a cobalt plating solution from a supplier if your needs are real.

I am not aware of anything especially dangerous about cobalt plating, as opposed to other plating processes. But most plating involves the use of aggressive, toxic, acids and alkalis; and the consequent needs for wearing protective gear and training in the safe handling of the chemicals.

The old truism is that 90 percent of plating is in the preparation. So if you are asking for general instruction in the whole process, as opposed to how to formulate a cobalt plating bath, there is a lot more to it than we can cover in a few paragraphs here. Please start with one of the "Must have" plating books. Good luck to you.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
(Ted is available for instant or longterm help)

2000

Although the text books say cobalt plating is very similar to nickel plating, don't believe them! Cobalt deposits tend to be much more highly stressed and many of the additives used in nickel plating do not have the same effect on cobalt. There is also a propensity for cobalt deposits to have hydrogen co-deposited, causing gas marks. Very thin coatings can be achieved, but anything of any decent thickness is much more difficult.

Cobalt has been accused of being a sensitising metal, like nickel. There may be some truth in this, but most of the sensitising tests are done with cobalt salts that contain nickel as an impurity. There appears to be an almost 100% correlation between people with nickel and cobalt sensitivity, so serious thought should be given to the adverse health claims.

Just one thought, why do you want to plate cobalt, wouldn't nickel be better (at least it is easier and much better known!)

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2000

---