Background: AZ91D is one of the most widely used die-casting magnesium
alloys. The corrosion processes of these materials is complex due to the simultaneous
action of metallurgical and surfaces states. Mapping the corrosion behavior
in chloride-containing aqueous solutions is of practical interest to guide the safe use
of magnesium alloys against deterioration and accompany the evolution of the electrochemical
response with time.
Methods: The corrosion behavior was assessed using electrochemical tests consisting
of potentiostatic polarization and potentiodynamic polarization for the AZ91D
alloy after immersion for up to 7 days in NaCl solutions with different chloride concentrations.
Results: A corrosion map was elaborated using the information obtained from the electrochemical tests.
Immunity, passivation and corrosion zones were identified. The chloride concentration strongly affects
the passivation range.
Conclusion: The corrosion region becomes wider as the chloride concentration increases at a given applied
potential. The surface oxide film is, therefore, protective in the most diluted solutions (0.01 M and
0.03 M) below -1.20 V and becomes more prone to pitting corrosion for more concentrated solutions.
The corrosion map evolved from 1 to 7 days of immersion, suggesting that transition between the different
zones can be affected by the exposure conditions.