Environmentally Induced Failure of Gold Jewelry Alloys

Abstract

Stress corrosion cracking (SCC) is an established form of environmental attack in low karatage gold jewelry alloys. The cause of failure is often attributed to exposure to chlorinated solutions. At a certain gold content (usually greater than 14K) the alloy is widely believed protected from SCC. In this study, three commercial 18K gold alloys (yellow gold, nickel white gold, and palladium white gold) were tested in combination with three different household solutions to determine relative corrosion rates. These rates were determined using polarization tests. Once the maximum corrosion rate had been established, SCC tests using the constant potential dead weight method were used to determine time to failure. The resultant failure surfaces were examined to determine mode of fracture, which in all cases was predominantly intergranular. It was found that corrosion rates depended upon both the alloy system and the test solution. SCC was clearly demonstrated in 18K gold alloys, although in all cases times to failure were significantly greater than has been reported for lower karatage alloys. Palladium white gold was far more resistant to SCC than the other systems studied.

The electrochemical corrosion behaviour of quaternary gold alloys when exposed to 3.5 % NaCl solution

“…Merriman and co-workers [23] reported the time to fracture during SCC tests was much higher for the 18 carat gold alloys (several hundred hours) compared with those for lower-carat gold alloys (several minutes). In addition, the corrosion rates of the low-carat gold alloys were attributed to selective dissolution of the alloying additions, whereby dissolution of Zn occurred initially, followed by dissolution of Cu, Ni and Pd, leaving a gold-enriched layer.…”