Corrosion behaviour of extruded AM30 magnesium alloy under salt-spray and immersion environments

• Quantification of AM30 corrosion mechanisms in two environments were obtained.
• Immersion environment caused higher general corrosion and pit nucleation rates.
• Sodium diffused regions around the corrosion pits acted as cathodic sites.
• Chemical heterogeneity of the aluminium content affected the filiform corrosion.

The mechanisms associated with general, pitting, and filiform corrosion were quantified at various intervals for extruded AM30 magnesium alloy exposed to a cyclical salt spray and immersion environment. The three mechanisms were quantified using optical microscopy, laser profilometry, and SEM coupled with EDX for over 60 h of testing. General corrosion and pitting corrosion were more severe in the immersion environment, and filiform corrosion was more severe in the salt-spray environment. The presence of a sodium ion (Na+) diffusion region around the edge of the corrosion pits functioned as cathodic sites, accelerating the localised pitting corrosion rates in immersion environment.