Abstract: The EIS of the anodic dissolution process of pure aluminum in an alkaline solution was fitted using an expression of Faradic admittance previously proposed by Cao[11-12], based on which the mechanism of the process was proposed. The results show that the capacitive loop in low frequency region of EIS is caused by the reaction of Al (ss), and the inductive loop in middle frequency region is caused by the reaction of Al(OH)ads. The time constants of Faradic admittance τ1 and τ2 mean the converting time of unit species Al(ss) and Al(OH)ads on unit bare surface site. Generally, τ1 and τ2 both decrease with the increase of the potential E.τ1 >0, τ2 >0, satisfy the conditions required by stability, and by Kramers-Kronig transforms as well. g1 and g2 relate to the variation of covering density of reactants Al(ss) and Al(OH)ads. g1< 0 indicates that the aluminum surface tends to be passive when the potential increases.

Key words: Pure aluminum, Alkaline solution, Anodic dissolution, Electrical impedance spectrum (EIS), Analysis