Influences of hydrostatic pressure on passivation and pitting evolution behavior of pure aluminum

This study employs electrochemical methods (open circuit potential, electrochemical impedance spectroscopy, cyclic polarization, electrochemical noise (EN)) and surface analysis techniques (scanning electron microscopy, X-ray photoelectron spectroscopy) to investigate corrosion evolution behavior of Al in 3.5% NaCl at 0.1 and 10 MPa. Results indicate that the influences of hydrostatic pressure on corrosion evolution behavior of Al is closely related to the activity of dissolved oxygen and Cl − . In the early stages, corrosion of Al is primarily governed by the passivation effect of oxygen. Increasing hydrostatic pressure enhances the activity of dissolved oxygen, promoting the formation of a passive film on Al surface, which improves passivation and pitting resistance of Al. In the later stages, the dense passive film isolates Al from dissolved oxygen, and corrosion of Al is mainly induced by Cl − disrupting the passive film and triggering pitting. Increasing hydrostatic pressure increases the activity of both Cl − and the passive film, accelerating the disruption of the passive film and reducing pitting resistance of Al. Results of EN analysis also show that increasing hydrostatic pressure increases the probability of pitting growth on Al, enhancing its pitting tendency.