Thick and Dense Anodic Oxide Layers Formed on Aluminum in Sulphuric Acid Bath

Thick and dense oxide layers were obtained on aluminium in sulphuric acid electrolyte. For this purpose, the methodology of experimental design was used. A three-variables Doehlert design (bath temperature, anodic current density, sulphuric acid concentration), was achieved. In order to maximize the growth rate and the density of the anodic oxide layer, optimum path study was conducted. Under the determined optimal anodizing conditions (5.7°C, 3 A·dm−2, Csul=140 g·L−1), the estimated response values were 0.86 μm·min−1 and 3.12 g·cm−2 for growth rate and density, respectively. The morphology of optimum layer was examined by scanning electron microscopy (SEM). The compactness of the optimum anodic layer can be correlated with its morphology revealed by SEM observations.