Anodic behavior of Mg in acidic AlCl3–1-ethyl-3-methyl-imidazolium chloride ionic liquid

• A viscous layer formed at Mg/ionic liquid interface after the dissolution of Mg.
• As direct evidence, photo of viscous layer at the interface was presented.
• Viscous layer was resulted from accumulation of dissolved Mg(II) at interface.
• Formation of viscous layer resulted in a homogenous etched Mg surface.
• Dissolution model of Mg and formation mechanism of viscous layer was discussed.

In this paper, anodic behavior of Mg in acidic AlCl3–1-ethyl-3-methyl-imidazolium chloride (AlCl3–EMIC) ionic liquid was investigated by conducting linear sweep voltammetry, chronoamperometry and chonopotentiometry. The viscosity of Mg dissolved ionic liquid and the surface morphologies of Mg were characterized using an Ostwald viscometer and a scanning electron microscopy, respectively. The results showed that the oxide film on the surface of Mg had great effects on the anodic behavior. The dissolution of Mg under anodic polarization occurred after the breakdown of oxide film. A viscous layer was observed forming at the interface of Mg/ionic liquid during the dissolution process. The formation of viscous layer was attributed to the accumulation of Mg dissolved AlCl3–EMIC ionic liquid at the interface, which was of high viscosity. With a viscous layer formed in the anodic process, the etched surface of Mg anode was homogeneous and flat without any etching pits. Otherwise, the Mg showed a morphology of pitting on the surface.