Influence of Heat Treatment on the Corrosion of the Al–Mg Intermetallic Alloy in Synthetic Seawater
Abstract
Highlights Mg migration promoted by heat treatment in Al−20 wt.% Mg alloy favors the formation of the phases α−Al(Mg) and β−Al3Mg2 Heat treatment modulates the β−Al3Mg2 intermetallic network in Al−20 wt.% Mg alloy β−Al3Mg2 distribution in Al−20 wt.% Mg alloy promotes susceptibility to corrosion Anodic (α) and cathodic (β) microgalvanic coupling promotes corrosion Abstract 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.