Mitigation of intergranular stress corrosion cracking in Al-Mg by electrochemical potential control

Abstract

Intergranular stress corrosion cracking is progressively mitigated in the Al-Mg alloy AA5456-H116 by establishing potentials anodic to Epit of the Al matrix, the phase, or both throughout slow rising displacement testing. Specifically, the relative value of the applied potential with respect to Epit (α) and Epit (β) determines whether the β breakdown activates the Al matrix (most severe IG-SCC), the β breakdown only occurs (intermediate IG-SCC severity), or both microstructural components are passivated (mitigated or no IG-SCC). Full immersion in NaCl and MgCl2 environments shows that this mitigation can occur over ranges of chloride content and pH, to varying degrees based on ionic solution severity.