Silvia B. Farina

Stress corrosion cracking of 18 carat gold

Abstract Due to the so-called “parting limit” in gold alloys there is a general belief that copper–gold alloys with a gold content above 40–45 a/o (atomic %) are immune to stress corrosion cracking (SCC) in aqueous solutions. In the present work it is reported that, by an adequate choice of the corrosive environment, it is possible to produce intergranular SCC in Au–Cu alloy of 18 carat gold, equivalent to Au 50 a/o, in aqueous solutions.

Stress corrosion cracking of zirconium and Zircaloy-4 in halide aqueous solutions

Abstract Zirconium and Zircaloy-4 in 1 M NaCl, 1 M KBr and 1 M KI aqueous solutions were found to be susceptible to stress corrosion cracking (SCC) only at potentials above the pitting potential. In all the tested systems the following steps were found: first electrochemical breakdown of the passive film, followed by intergranular attack due to anodic dissolution assisted by stresses; and finally a fast transgranular propagation. This last step was identified as the “true” SCC process. The analysis of the possible mechanisms involved during this process led to the conclusion that the surface-mobility SCC mechanism can be used to explain the experimental results found in the present work.

Stress Corrosion Cracking of Zirconium and Zircaloy-4 in Iodine-Alcoholic Solutions

Abstract Stress corrosion cracking (SCC) susceptibility of Zr (UNS R60702) and one of its alloys, zircaloy-4 (UNS R60804), was studied at room temperature in 10 g/L iodine dissolved in various alcohols: methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-octanol. SCC was observed in all the systems studied and the crack propagation rate was found to vary depending on the size of the solvent molecule. As the solvent molecular weight increased, the crack propagation rate decreased. Prior to crack propagation, intergranular attack was found in all the solutions tested. The intergranular corrosion rate also varied according to the size of the solvent molecule. Since the corrosion rate of Zr single crystals was similar in all the solutions tested, it was concluded that the decrease in both the intergranular attack rate and the crack propagation rate was attributable to a steric effect that hindered the access of the corrosive species to the tip of the crack. The surface-mobility SCC mechanism accounts ...