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Will rhodium plated stainless meet European nickel-free standard?
Q. Under the European Nickel Free Standard EN 1811 [affil. link to spec at Techstreet].1999, for stainless steel bracelet coated with rhodium, it is likely to exceed the limit of 0.5 µg/cm2/week? If we processed the stainless steel through stamping, drilling, disassembling, etc., will it increase the chance of nickel release? How could it be solved then? Is it possible to remove the excess (small in quantity) nickel by potassium cyanide solution?
Thanks for answering.Heidy Sung
Plating factory - Milan, Italy
A. There is no precise answer to your problem as you have posed it. Firstly, the release of nickel from stainless steel is possible, but can be avoided by using a stainless steel that doesn't contain nickel, such as using 400 series materials. Secondly, the release of nickel from s/s that does contain nickel will be dependent on the ability it to get through the overplate. If the rhodium is sufficiently thick and continuous, it will not get through, but if it is discontinuous, no matter how thick it is, you will still get nickel release. Thirdly, if the rhodium wears off due to abrasive wear, no matter how continuous it originally was, the substrate, if it contains nickel, could release it. There has been a lot of work done with European supply houses to provide barrier materials such as white bronzes that will minimise the release of nickel, so ask your supplier.
R&D practical scientist
Chesham, Bucks, UK