Corrosion Inhibition of Mg Alloy ZEK100 Sheet Metal by Dissolved Lithium Carbonate

The extent of corrosion inhibition of Mg alloy ZEK100 in 100 mM NaCl (aq) imparted by dissolved Li2CO3 (aq), with a particular focus on Li incorporation into the surface film that forms under activated anodic dissolution (anodic polarization) was determined. Dissolved Li2CO3 reduces corrosion by a factor of ∼12 when added at a concentration (100 mM) just below saturation. Effective inhibition involves suppressing the transition to filament-like corrosion, and associated anode/cathode activation, initiating at local breakdown sites. Such suppression is linked to the formation of Li-doped MgO as a corrosion product film during activated anodic dissolution. When formed by anodic polarization, the film composition also significantly affects the chloride ion distribution with the film. Without Li incorporation, chloride ions tend to enrich at the film/metal interface, whereas with Li incorporation, chloride ions tend to be uniformly distributed within the film.