Nickel Release of 10 K White Gold Alloy for Jewelry

Abstract Nickel is widely used as a bleaching element in white gold alloys for jewelry, it helps to obtain good color and mechanical properties. Although master alloy suppliers promise the safety of their products, the nickel allergy cases caused by such white gold jewelries are reported now and then. The purpose of this study is to investigate nickel release rate of a so-called “No nickel allergy” 10 K white gold alloy extensively used for jewelry and its potential risk to cause nickel allergy. The samples were processed by different heat treatment conditions and surface treatment methods, their nickel release rate were tested according to EN1811 standard. The results show that nickel release rate is closely related to the corrosion resistance and changes under different processing conditions even for the same material. The nickel release rate sequence (from big to little) is as follows: “annealing at the two-phase region with rough surface > cold working with rough surface > cold working with polishing surface > quenching with rough surface > quenching plus low temperature tempering with rough surface”. Although the adjusted values of nickel release rate under various process conditions met the requirement in nickel Directive “94/27/EC”, most of them fail to meet the requirement specified in “2004/96/EC” for piercing jewelry, and the actual values obviously markedly exceed both Directives. There would exist nickel allergy risk for jewelries made from this material, especially for puncture accessories