Discovery bu kinetic studies of the latent physicochemical processes and their mechanisms during the grwoth of porous anodic alumina films in sulfate electrolytes

摘要

The kinetic of growth of porous anoidc alumina films in pure H_2SO_4, in mixtures in H_2SO_4 and Al_2(SO_4)_3 and in Al(HSO_4)_3, NaHSO_4 and KHSO_4 electrolytes were studied. The latent physicochemical processes at the pore base surface/electrolyte interface, across the barrier layer, inside the metal/oxide interface and at the pore wall surface/electrolyte interface and their mechanisms were revealed. High field strength equations were formulated describing the ionic migrations from the pore base surface. These showed that, at constant current density and temperature, the inverse of the pore base square diameter depends linearly on the inverse of the H~+ activity in the anodizing solution and that this diameter increases with H~+ activity, in agreement with the experimental results. The mechanism of electrolyte anion incorporation inside the barrier layer and the real distribution of the anion concentration across both the barrier layer and pore walls were deduced. The effects of the different kinds and concentration of the electrolyte anions and cations on both the above processes and their mechanisms were also examined.