Using cobalt plating to obtain nickel-free plating

A. To be nickel free, you have to change nickel to cobalt everywhere you see nickel in the bath makeup. That means in both chloride and sulphates or sulfamate if you were using that bath. Is it feasible? By what criteria? It costs more and is not as readily available. Cobalt prices have had a wider variability in prices than nickel, which has had massive swings in the price over the last 40 years.

A. To be nickel free, every nickel source has to be replaced by cobalt. Don't believe that you can simply change nickel for cobalt and expect the same quality of deposit - it isn't true. For instance, there are two common crystal structures for cobalt that have a low transition temperatures and this can cause problems. Also, lots of the brighteners used with nickel don't work with cobalt. You may also get into problems with deposit stress.

A. Gentlemen,

The Swiss have banned Nickel as an undercoat for Gold, and overlooked Cobalt. Does this mean cobalt deposits under Gold do NOT sensitise human skin? And does its absence in the Ban certify it as Non Sensitising for skin? I suggest that White Bronze is used to replace Nickel to obtain Nickel-Free, Non Irritating deposits which do NOT sensitise human skin in the spirit of the Swiss Ban. White bronze accepts Gold readily.

Regards,

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! Hi Asif. I don't know if cobalt sensitizes human skin, and I suspect that Mssrs. Tio, Watts, and Crichton don't know either. But you seem to be implying that it does (by alluding to the 'spirit' of the Swiss ban). If you know it to be true, or have reason to suspect it, or you can point us to literature that considers the issue, please do so. Thanks!

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

Ted,

Mr Nurie is correct in suggesting a good solution to the nickel problem is white bronze. However, it is not only Switzerland that has banned the use of nickel in jewellery, the whole of the European Union has done so and it is illegal to sell any new jewellery in the EU that contains more than 0.05% nickel or releases more than 0.05 ug/cm*2/week. This is all very well documented by the Nickel Development Institute (NiDI.org), who should be consulted for the definitive work on the subject. The question of cobalt is not so clear; cobalt is an essential trace element, but (at least in the UK) there is some evidence from dermatological patch testing that cobalt can induce eczema. However, saying that, the figures I have seen for this show that the cobalt salts used contained in excess of 75 ppm nickel. It has been shown that nickel levels as low as 40 ppm can induce eczema in people who are already sensitized to nickel, so personally I would not hold too much faith in these tests.

Some cobalt salts are known to be harmful to man, but overall, I would suggest that at present the jury is out on the true effects of cobalt on the skin. However, seeing how the EU legislation system moves, I would not be surprised if sometime in the not too distant future cobalt got identified as being potentially harmful and therefore banned from being used in products such as jewellery.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004

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Thanks, Trevor, I knew that the European Union had banned nickel in jewelry. Personally, I applaud that, and I wish American platers and manufacturers would be less reactionary on this subject and do the same. If cobalt presents more or less the same problems, I'd personally be happy to see it banned as well. But if it doesn't, I'd rather not see it tarred by association (as happened to chromium plating by association with hexavalent chromate finishes). I'm only asking because Mr. Nurie seemed to me to be condemning cobalt as being the same as nickel by speaking of the 'spirit' of the rules.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

A. Hi Inga. I have seen in print that 40 percent of adult women under 30 are sensitive to nickel, and 30 percent of women 30 to 40 years old are sensitive, etc.

Once you have the allergy you have it for life, so it is important that this not be misread as an indication that sensitivity goes down with age, but rather that exposure has gone up among younger women (probably primarily due to body piercings).

Whether the survey numbers are exactly accurate, though, doesn't seem to me to be the salient point. Rather, the point is that the numbers are huge and skyrocketing, the allergy is acquired, and it seems strongly proportional to exposure. It is possible that virtually all of us would acquire the allergy if we wore nickel plated piercings for years. I believe it is urgent that we do everything we reasonably can to get nickel out of jewelry as rapidly as practical.

Hi Kishor. Can you please try to phrase your question in terms of the discussion that has already taken place, because I can't quite understand it. It has already been suggested that cobalt is a possible substitute for nickel; and it has also already been suggested that white bronze plating is a substitute.

I also am not sure whether your jewelry is made of silver and you wish it to look like gold, or whether it is made of baser metals and you want it to look like silver. Please work hard to keep moving the discussion forward. Thanks!

Regards,