Structural properties of electrochemically designed porous oxide films on AlMg1

Abstract The characteristics of electrochemically formed porous oxide layers on aluminium alloys were investigated. The anodizing conditions were varied in a broad range (electrolyte: sulfuric acid, phosphoric acid and mixtures from these, concentration: 0.3–2.0 M, voltage: 5–10 V, time: 30–90 s, temperature: 25–50°C). The oxide layers were characterized via spectroscopic interference measurements to determine the oxide thickness. The morphology of this layer was also observed by AFM. The structural parameters of the oxide layer were characterized by electrochemical impedance spectroscopy (EIS). An equivalent circuit comprising two layers of barrier and porous layers was used to determine the characteristic parameters. The growth rate of oxide varied with electrolyte type, temperature and concentration. The proportionality constant of the barrier film thickness in relation to the applied voltage and the relative porosity of the film were calculated from this model. Three-dimensional response surfaces were constructed with the aid of an appropriate experimental design strategy which allows the study of not only the effects of the fabrication variables but also the interactions between these variables.