Stress Corrosion of α-Brass in an Acid Sulfate Solution

Single phase, Cu-30 At % Zn specimens, which were anodically polarized at 0.24 V (SHE) (⁠ 10⁻⁴ A cm⁻²) in acid Na₂SO₄ solution at 23 C (73 F), were found to undergo stress corrosion cracking (SCC) during elongation. The fracture path was mainly along grain boundaries, with some secondary cracking through the grains. The fracture surfaces exhibit metallic luster and deformation markings, indicating that fracture occurred in the absence of thick reaction product films. The results show that the ammonium ion and other complexing ions are not necessary for stress corrosion of α-brass. They support the idea that preferential anodic dissolution, which is enhanced at the crack tip by dislocation motion, may be important to the stress corrosion process.