Structural, chemical and optical characterization of AAO layers electro colored by copper and tin sulphate salts

Aluminum is preferred for many engineering applications because of it is high mechanical strength, chemical stability, low density and low working cost. In addition, aluminum is high conductive material both electrically and thermally. Aluminum always maintains a thin (3-5 nm) oxide layer on its surface depending on the ambient conditions. The corrosion resistance of this thin oxide layer is limited therefore; it not enough to protect the base material in aggressive environments.The pores in the AAO layer which is produced by H2SO4 anodic oxidation enables to usage in the decorative applications. The procedure of the electrolytic coloring of AAO layer is made in the baths that involves various metal salts such as (SnSO4, Cu SO4, NiSO4, CoSO4 ect.) The metal ions deposits at the bottom of the pore by the effect of voltage applied during the coloring process. In the literature, there are some contradictory information about the metal phase which is deposed at pore bottoms. Whether the phase deposited inside the pores bottom is oxide or metallic is controversial. However, most research imply the metallic phase is deposited. In this study, chemical, structural, and optical analyses are fulfilled to identify the metal structure which is deposited at the bottom of the pore. First of all XRD analysis are performed to specimens, which are uncolored, colored with tin and copper. According to XRD pattern, the structure at the pore bottom, may be both oxide and metal mixture. In order to verify the XRD data, XPS analysis are performed. The XPS data are showing that the structure, which is deposited in the pore, is a mixture of metal and oxide. XPS analysis have been done on colored AAO layers, which were separated from aluminum base. Final data are proving the fact that a Sn/ SnOx and Cu/CuxO mixture had deposited into pore. Optical analysis have shown both AAO layers' thickness and coloring time are critical ofthe final color of AAO layer. The color is getting darker with the increasing amount of Me/MeO which deposited in the bottom of the pore. If the amount of deposition is changed, the wavelength, which corresponded to absorption edge, is changed as well.