Abstract: Al plating was electrodeposited on cupronickel alloy as substrate in the trimethyl-phenyl-ammonium chloride and anhydrous aluminum chloride (TMPAC-AlCl3) quaternary ammonium room temperature ionic liquids with benzene used as solubilizing assistant. The effects of current density and plating time on surface microscopic morphology and cathodic current efficiency were studied. The corrosion resistance of the as-deposited Al layer was evaluated by potentiodynamic polarization measurements. Moreover, scanning electron microscope, energy dispersion X-ray spectrometer and X-ray diffraction were used to characterize the samples. The results showed that the as-deposited Al plating obtained at 15 mA/cm² for 30 min has a compact surface. Its cathodic current efficiency exhibits a maximum value up to 92% and decreases with increasing plating time mainly because of the precipitation of AlCl3 on the surface of Al anode. The polarization measurements showed that the thicker the Al plating, the higher the corrosion resistance of the plating. Moreover, the anodic passivation behavior of the as-deposited Al plating (17 μm thick) was found, which can effectively protect the substrate from corrosion.