SUMMARYElectrochemical measurements, recorded during the growth of the duplex layer, in combination with high voltage electron microscopy, were used to investigate the influence of pretreatment on the formation of the porous oxide film. The growth was studied of the porous layers on relatively rough surfaces, prepared by three different pretreatment processes: rolling, mechanical brushing and AC electrochemical etching. These treatments introduced topographical and compositional heterogeneities on the surface. HVEM examination of the Al2O3/Al interfaces showed that the steady-state anodic morphology, consisting of hexagonal cells, with a central pore, was valid on all types of substrates. Pore initiation was related to the substrate pretreatment.
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