Stress corrosion cracking of α-brass in phosphate, triphosphate and pyrophosphate solutions

Abstract

The constant potential slow strain rate technique was used to study the susceptibility of α-brass to stress corrosion cracking (SCC) in phosphate, triphosphate and pyrophosphate solutions. α-Brass was found to be immune to SCC in alkaline Na 2HPO 4 solutions, but susceptible to SCC in alkaline Na 4P 2O 2 and Na 5P 3O 10 solutions. Only intergranular cracking was observed. The presence of Cu 2+ ions in the corrosive environment expanded the range of electrode potentials where SCC was found. At constant potential, the presence of Cu 2+ ions had no effect on crack velocity. The Cu 2+ ions acted by reducing the IR drop in the crack, thus allowing for higher electrode potentials at the tip of the crack. The present results fit better into a surface-mobility SCC mechanism than into an anodic dissolution mechanism.