Abstract
Strained electrode reactions of 5083 alloy in 5.3%NaCl + 0.3%H2O2 aqueous solution were studied as functions of tensile stress, strain, electrode potential, solution pH and microstructure. The susceptibility to stress corrosion cracking can be rapidly evaluated by means of a constant strain rate method under potentiostatic control. The shape of current/strain curves shows that the anodic dissolution is controlled by the rate of oxide film rupture and by the subsequent rate of repassivation. The grain boundary with β precipitates is attacked at lower potential and by application of strain less than that in grain body. The alloy more sensitive to stress corrosion cracking shows extended difference in breakdown potential between grain boundary and grain body. The breakdown potential for grain boundary corresponds with the critical potential for stress corrosion cracking. Typical stress corrosion cracking occurs in the potential range over this potential and below the breakdown potential for grain body. The anodic current density at the crack advancing edge is sufficient to account for the observed crack propagation rate. The stress corrosion cracks advance pricipally by electrochemical anodic dissolution.
