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Pure Cobalt Plating Problems & Solutions
Q. Recent experiments on pure cobalt electroplating employed a solution system comprising cobalt chloride hexahydrate (60 g/L), boric acid (20 g/L), and sodium dodecyl sulfate (0.3 g/L), operated at 70 °C with a current density of 40 mA/cm2 and pH 2.
The resulting electrodeposited cobalt exhibited dendritic crystal morphology with a hardness of 240 HV, contrasting with the favorable columnar crystal structure typically achieved in pure nickel electroplating. This dendritic microstructure resulted in virtually no tensile plasticity in the cobalt deposit.
What approaches could be implemented to address this issue?
- Nanjing Jiangsu
August 21, 2025
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Q. 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 ChanHKUST - Hong Kong
2000
A. 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 probably quite similar to 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 either here or in books to formulate your own solution that is really the equal of commercially available processes; rather, you should try to buy a cobalt plating solution from a supplier if your needs are practical. If you find none available, or your interests are more theoretical, you probably have a lot of development work ahead.
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 a general instruction in the whole process, please start with one of the "Must have" plating books. Good luck to you.
Ted Mooney, P.E.
Striving to live Aloha
(Ted can offer longterm or instant help)
finishing.com - Pine Beach, New Jersey
A. 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
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