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Alternative to Nickel plating

 

Since there's a regulation on Nickel emission for EU, so we (we're a jewelry manufacturers) switch to a copper-tin based plating instead of Ni. What is the property of such plating? and is there other Ni free alternative around?

WY Wong
- HK

Questions like this scare me. If cyanide was taken away from me, I'd want to quit the metal finishing business, because it is such an incredibly powerful tool. I can't even imagine having nickel baths taken away from me. There's no need to ban or regulate plating chemistry; we run a completely closed-loop cyanide system using ion-exchange columns. Lawmakers need to communicate and understand what industries do before passing reactionary legislature!

Michael Brewington
- Salisbury, Maryland, USA

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It is well known that nickel can present a health problem when people become exposed to it. Nickel has not been banned by the EU except in uses where it is in intimate and prolonged contact with the skin. This is clearly aimed at the jewellery and similar industries. The legislation refers to release rates of nickel from the offending article and as long as the release of nickel is below 0.5 µg/cm2/week the article can be sold; if it exceeds this rate, it is illegal to sell the article.

The purpose of the legislation is to minimise the chance of wearers of nickel-containing metal objects becoming sensitised to nickel. The initial problem will be manifested as eczema, but this can rapidly change into dermatitis and ultimately to sensitisation. Once a subject is sensitised, allergic responses can be triggered by nickel concentrations as low as 40 ppm.

Nickel sensitisation was originally thought to be a "female only" problem, as it was first seen in the 1930's when women wore nickel plated bra clips and suspender belts to hold up their stockings; however, with the increased use of (mainly) cheap jewellery by men and women, the problem has got worse and is now seen in both sexes. The percentage of the population who may suffer from this complaint varies, depending on the research publication sited, but as a general guide line, for western world caucasians, about 8-15% of the population are thought to be susceptible to the problem. Other nationalities and zones may have differing rates. It is not fully understood why this is so, but one theory suggests it could be due to differences in the pH of the skin and its secretions.

In conclusion, the legislation is not there to put an increased burden on the nickel industry, but to protect the health and welfare of the metal-wearing general public.

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

About the Ni emission requirement I do understand it's for the health of the general public, and we're trying everything we can to meet it (that's why I'm here) but sometimes getting the balance between meeting the law, and still maintain the quality is not that easy, not to mention having to meet target price. We uses Ni underplating for our product (Ni as a top layer was never an option) and on top we have Au or Pd, we've heard using at least 3 mic of those if we are to avoid the Ni problem, but that's not economically viable. We have replaced the Ni layer with a Sn/Cu alloy, but there's not enough information around for the performance for such plating and we are not sure what to expect of the plating, the last thing we want of course, is complaints from the customers. I'm sure our customers are happy to know that the products are safer, but they won't be too pleased if it comes at a price!

WY Wong
- Hong Kong

I would not advocate using thicker coatings of Au or Pd as this will make the product prohibitively expensive. You are right in going along the Sn/Cu route, but I would suggest you ask the supply house for performance details. It is worth mentioning that if the article contains nickel and comes within the remit of the legislation, it must comply with the release rate criteria; furthermore, in some EU countries (such as Germany, Sweden and Denmark) any products that contain more than a prescribed level of nickel must say so on the packaging. The bottom line is that nickel is best avoided in jewellery for sale within Europe.

I can also suggest you contact NiDI as they have been very active in this area in recent years. Alternatively, try contacting the Jewellery Manufacturers Association in the UK. Also in the UK, Engelhard have been very active in seeking alternative interlayers.

Finally I remember seeing somewhere that similar regulations were being considered by Japan and some other Pacific rim countries, but I only saw this once and cannot recall where. on the other hand it could have been a figment of my imagination! I would suspect that nothing has yet come if this idea in these areas.

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

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One possible alternative to copper-tin alloy as an under plate for jewelry is bright acid copper with palladium plate as a barrier.

Thank you Trevor for your very informative follow up. It has been suggested that the cause of the nickel sensitivity is nickel bearing earring posts in direct contact with the subject's blood in newly pierced ears. This theory would explain the condition being more common with women and the recent increase of the problem occurring with men.

Neil Bell
Red Sky Plating

Albuquerque, New Mexico

 

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