Influence of Heat Treatment on the Corrosion of the Al-Mg Intermetallic Alloy in Synthetic Seawater.

In this study, an Al-20 wt.% Mg alloy was synthesized to systematically correlate its electrochemical behavior in synthetic seawater with the microstructural evolution induced by heat treatment at 190, 300, and 350 °C for 6 h. The samples characterized by SEM and XRD reveal a progressive morphological evolution of the β-Al3Mg2 intermetallic phase. The open circuit potential, the potentiodynamic polarization and the electrochemical impedance spectroscopy showed that this microstructural evolution increased the microgalvanic corrosion, promoting passive-film breakdown, and reducing charge-transfer resistance. The Al-20 wt.% Mg alloy treated at 350 °C exhibited the highest corrosion current density, associated with β-Al3Mg2. These results demonstrated that controlling beta-phase precipitation through heat treatment provides an effective approach to tune the electrochemical behavior of high-magnesium aluminum alloys.