The passivation behavior of Fe in the acidic AlCl_3-1-ethyl-3-methyl-imidazolium chloride(AlCl_3-EMIC) ionic liquid was studied by linear sweep voltammetry and chonopotentiometry. Various approaches were used to characterize the composition and morphology of passive film formed on the Fe electrode, such as scanning electron microscopy(SEM), Raman spectra and X-ray Photoelectron Spectroscopy(XPS). The results showed that the critical passivation potential of Fe shifted to more negative when the molar ratio of AlCl_3:EMIC changing from 2 to 1.3.A film with a light yellow color was observed on the surface of the Fe electrode after passivation. The composition of the passive film was demonstrated to be FeCl_2. The passive film was composed of particulate FeCl_2 with average diameter of about 500 nm. The formation of FeCl_2 film was attributed to the variation of the electrolyte Lewis acidity from acidic to neutral at the interface during the dissolution process of Fe. The reason caused the variation of the electrolyte acidity was discussed.
The anodic behavior of neodymium in acidic AlCl3-1-ethyl-3-methyl-imidazolium chloride （AIC13-EMIC） ionic liquid was investigated by conducting linear sweep voltammeter and chonopotentiometry. The viscosity of Nd dissolved ionic liquid and the surface morphologies of Nd were characterized using an Ostwald viscometer and a scanning electron microscope, respectively. The chemical composition of Nd surface was indentified by Raman spectra. The results showed that dissolution of Nd under anodic polarization occurred after the breakdown of oxide films. A viscous layer formed at the interface of Nd/ionic liquid during the galvanostatic process of 5 and 20 mA/cm^2. The formation of viscous layer was attributed to the accumulation of Nd dissolved AlCl3-EMIC ionic liquid, which had high viscosity. The oxide films could be removed thoroughly and the surface of Nd was homogeneous without etching pits, when viscous layer formed in the anodic process. Otherwise, the surface showed a pitting morphology.
