Mitigation of Intergranular Stress Corrosion Cracking in Al–Mg by Electrochemical Potential Control

摘要

Abstract Intergranular stress corrosion cracking in the Al–Mg alloy AA5456-H116 is suppressed via cathodic polarization in 0.6?M NaCl, saturated (5.45?M) NaCl, 2?M MgCl2, and saturated (5?M) MgCl2. Three zones of intergranular stress corrosion cracking (IG-SCC) susceptibility correlate with pitting potentials of unsensitized AA5456-H116 and pure β phase (Al3Mg2) in each solution. These critical potentials reasonably describe the influence of α Al matrix and β phase dissolution rates on IG-SCC severity. Complete inhibition occurred at applied potentials of ?1.0?V and ?1.1?V versus saturated calomel electrode (V SCE) in 0.6?M NaCl. Whereas only partial mitigation of IG-SCC was achieved at ?0.9 V SCE in 0.6?M NaCl and at ?0.9, ?1.0, and ?1.1 V SCE in the more aggressive environments. Correlation of pitting potentials in bulk environments with IG-SCC behavior suggests an effect of bulk environment [Cl?] and pH on the stabilized crack tip chemistry.]]>