Effect of the local electric field on the formation of an ordered structure in porous anodic alumina

Experimental data and a model are presented, and the electric field that appears in porous alumina during electrochemical anodic oxidation of aluminum in electrolytes based on an aqueous solution of oxalic acid at a voltage of 90–250 V is calculated. It is found that the electric field in the layers with a porosity of 1–10% in growing alumina reaches 10$^9$–10$^{10}$ V/m, which exceeds the electric strength of the material and causes microplasma patterns emitting visible light at the pore bottom, the self-organization of the structure of porous alumina, and the anisotropy of local porous anodizing. Moreover, other new effects are to be expected during aluminum anodizing under the conditions that ensure a high electric field inside the barrier layer of porous oxide.