Prevention of nickel release from electroplated articles in the context of allergic contact dermatitis: further outcomes

Abstract

‘Nickel Allergy’ sometimes occurs when nickel-containing articles are in direct and prolonged contact with the skin, leading to corrosion of elemental nickel by sweat, liberating sufficient nickel ions to be absorbed through the skin and initiate an allergenic effect. EU ‘Nickel Restrictions’ impose limits on the amount of nickel released from articles intended for use in this application but permits a non-nickel surface coating that can ensure the rate of nickel release does not exceed 0.5 μg cm−2 week−1 after 2 years of normal use. The official tests for coated items are simulated wear and corrosion under EN 12472 followed by determination of nickel release under EN 1811, and articles shall not be placed on the market unless they pass these tests. A paper published in Transactions during 2015 reported bright nickel coatings with top coats that would prevent nickel release and pass these tests. Regular chromium deposited from a hexavalent electrolyte was the benchmark, with microporous chromium and supplementary organic coatings evaluated for improved performance. All prevented nickel release, but the best low-cost commercial coating was regular (conventional) chromium deposited from a hexavalent electrolyte. Further tests reported here were conducted to evaluate bright nickel deposits with top coats of tin–cobalt alloy, and of hexavalent chromium with supplementary coatings of coloured physical vapour deposition and electrophoretic coatings. Tests with trivalent chromium top coats deposited from proprietary chloride and sulphate electrolytes showed that regular (conventional) chromium over bright nickel failed the nickel release test. But microporous trivalent chromium deposits passed the tests satisfactorily.