Influence of Experimental Test Conditions on the Ni Release of a Cu‐Ni Alloy in Artificial Sweat

Nickel allergy is a problem for an increasing number of persons. In 1994 the European Commission published the "Nickel directive" 94/27/EC that defines the maximum Ni release amount of objects in prolonged contact with skin (0.5 µg/cm2 week). To implement this directive reliable test methods have to be established to check the quality of consumer products. Essential is the selection of the correct experimental test conditions. These include the definition of an artificial solution that simulates natural sweat. Different types of artificial sweat composition are described in the literature. Some test standards are ready, such as EN 1811. In the present study the solution suggested in EN 1811 was taken as a basis. As test material a CuNi25 (wt.%) alloy was chosen because of its use in Euro coinage. The influence of pH and compounds such as urea, lactic acid, ammonia on the corrosion behavior has been investigated using electrochemical methods. The quantitative analysis of Ni release after immersion test was performed by polarography with stripping analysis. Immersion tests were performed according to the EN 1811 procedure. The results support a better understanding of the relevance of various experimental factors on Ni release from materials in contact with artificial sweat.