Aluminum (Al) coatings, which are found to be dendrites, have been deposited on uranium (U) substrate in ionic liquid via galvanic displacement. Interestingly, a dense Al nano-layer has formed between the Al dendrites and the U substrate. In this work, the growth mechanism of the Al coating has been investigated by ultraviolet-visible spectroscopy, scanning electron microscopy, grazing incidence X-ray diffraction, and electrochemical measurements: the galvanic reaction sees the oxidation of U from the substrate while Al2Cl7 (-) are reduced on its surface, driven by the electrochemical potential difference between Al and U. Furthermore, we have found that the Al nano-layer passivates the uranium surface, which is proved to be the rate limiting step in the galvanic deposition process; the observation of the interface morphology evolution process indicates that this Al nano-layer grows in a three-dimensional mode. This work demonstrates a convenient approach to deposit dense Al nano-layer on U, without any external power source. [GRAPHICS] .