Interference colors of thin oxide layers on titanium

This work deals with the characterization of the color properties of different titanium oxide films, obtained by means of anodic oxidation. The color of these oxides varies with film thickness, since it is due to light interference phenomena taking place at the metal-oxide-air interfaces. Color measurements were carried out by using spectrophotometry techniques: the values obtained belong to the colorimetric space CIELAB, which is defined as standard colorimetric space. The results of these analyses were related to the oxide structure, analyzed with X-ray diffraction techniques, which was determined to be either amorphous or semicrystalline. Also the oxide thickness was taken into account. This feature was derived both from ellipsometric data and from reflectance spectra: the two data are shown to be in good adherence. Both commercial purity titanium (grade 2 ASTM) and titanium alloy Ti-6Al-4V substrates were investigated.