Effect of Oxyanions and Chloride Ion on the Stress Corrosion Cracking Susceptibility of Admiralty Brass in Nonammoniacal Aqueous Solutions
SourceThe stress corrosion cracking (SCC) susceptibility of admiralty brass in several nonammoniacal solutions of pH ∼8 has been investigated at 25 °C using the slow strain-rate technique. The SCC tests were made at a controlled potential of 300 mVH. This potential is close to the cupric oxide/cuprous oxide (CuO/Cu2O) equilibria, in near neutral solutions (6 < pH < 8), on the potential-pH diagram of copper. In the present study, cracking occurred in several solutions; the severity of the cracking depended upon the type of anion present in the test solution. The order of anions in decreasing tendency to promote SCC in admiralty brass was: NO2- > NO3- > ClO3- > SO4= > MoO4= > Cl- > WO4= > HCO3- > B4O7= > CrO4=. The estimated crack velocity ranged from high values of the order of 10-7 m/s in the nitrite solution to no cracking in the phosphate and the solutions following it in the above series. The cracking was always transgranular with considerable branching in some cases.