Effect of cations on stress corrosion cracking: Ag-40Cd alloy in silver ion aqueous solutions containing a variety of foreign cations

Uhlig showed that cupric ions accelerated the stress corrosion cracking (SCC) of α-brass in ammoniacal solutions. When adding foreign metal cations (cadmium, zinc, cobalt and nickel) to the solutions, it was found that only the copper ion had an effect on the fracture time. The aim of the present work was to study if this is a more general phenomenon in SCC. To that purpose, a Ag-40Cd (at/o) alloy was strained in silver nitrate aqueous solutions containing a variety of foreign metal cations, at the equilibrium potential of the reaction: Ag+ + e− = Ag. SCC was found in all cases. Silver ions specifically accelerated the crack propagation rate and the addition of foreign cations showed no significant effect on the phenomenon. Most of the cracks found were intergranular, and the specific effect of the cations could be explained through the surface mobility SCC mechanism.