In situ electrochemical dissolution of the oxide barrier layer of porous anodic alumina fabricated by hard anodization

An innovative electrochemical approach was developed for reducing or eliminating in situ the oxide barrier layer from the pore bottom tips of anodic aluminium oxide films. The procedure was based on including in the usual anodization process additional steps of re-anodization at constant current density, and whose current density halves from step to step. In this way, we managed to completely remove the oxide barrier layer in samples fabricated by the hard anodization procedure in oxalic acid at 120 V. By generating a suitable disturbance when the system is in steady state, we can modify the relationship between the oxide formation and dissolution rates for the aluminium–alumina-electrolyte system. The resulting structure (porous alumina with open pores) remains on the aluminium substrate after the process has been carried out, so this method could be used to fabricate a transfer mask for developing new devices. This study could provide new bridges towards novel applications of anodic aluminium films in such fields as electronics, magnetics or sensors.