Nonsensitizing Zr–O–N Coatings for Jewelry Made of Nonprecious Alloys

Abstract

In recent decades, jewelry manufacturers have started using nonprecious alloys to decrease production costs. A large number of customers, however, have an allergic (sensitizing) body reaction to jewelries made of such materials. The application of nonsensitizing coatings can decrease the negative influence of the jewelry material on the human organism. One material biologically inert towards human body tissues is zirconium. In this study, zirconium-based coatings applied by magnetron sputtering are examined. Eleven regimes of applying zirconium oxynitride coatings onto a substrate of AISI 430 grade steel are investigated. Microhardness and corrosion tests of the coatings in Hank’s solution are conducted and color performance is determined in the CIE 1976 L*a*b* and RGB color spaces. The coating width is 0.4–1.2 μm. It is established that the coatings have a microhardness of 2.5–3.0 GPa and are able to imitate colors of jewelries. Using energy dispersive X-ray spectroscopy, it is established that the coatings consist of Zr, N, and O. The authors select sputtering conditions that produced metallic coatings with high optical reflectance in an energy range near the infrared region of the spectrum (<1.7 eV) of golden color with high lightness. It has been experimentally proven that the coatings do not corrode in Hank’s solution. The allergy patch test of jewelry with the zirconium oxynitride coating conducted on a respondent with sensitizing reaction to nonprecious alloy jewelry has demonstrated a good result—no signs of skin allergy were observed. The results allow us to recommend magnetron sputtering as a technique for applying zirconium-based coatings onto jewelry of nonprecious alloys.