Prevention of nickel release from decorative nickel-chromium electroplated articles in the context of allergic contact dermatitis

Abstract

'Nickel Allergy' arises when some nickel-containing articles are in prolonged and direct contact with skin, causing corrosion of elemental nickel by sweat and liberating sufficient nickel ions to be absorbed through the skin, resulting in an immune reaction in the form of allergic contact dermatitis (ACD). The EU 'Nickel Restrictions' legislation imposes limits on the amount of nickel released from articles intended to come into direct and prolonged contact with skin, but permitting a non-nickel surface coating that can ensure the rate of nickel release does not exceed 0.5 μ/cm2/ week after two years of normal use. Tests for qualification are EN 12472 and EN 1811. A program of testing was undertaken to determine nickel release rates from electroplated bright nickel-chromium coatings, with and without UV cured clear protective top coats suitable for use on moulded ABS plastics substrates. Regular chromium deposited from a hexavalent electrolyte was used as the benchmark, with microporous chromium, electrophoretic and sprayed Sol-gel coatings evaluated for potentially improved performance. While all these coating combinations over bright nickel significantly decreased nickel release, regular (conventional) chromium was the coating of choice, given its ready availability worldwide, and lowest cost. Recognising environmental constraints on hexavalent chromium in Europe and other countries, substitution by trivalent chromium was reviewed and pointers identified for the selection of commercial processes that will provide a regular chromium deposit with suitable protection over bright nickel.