Effect of Surface Finish on the Colour Anodising of Ti-6al at Various Voltages

Abstract

In this study, the colour anodising of a Ti-6Al-4V alloy in 0.05 M H3PO4 was investigated in the voltage range of 40-100 V. The Ti-6Al-4V substrates were anodised under two initial surface conditions: ground and unground. By means of ground samples, the native oxide layer was removed before anodising using conventional mechanical grinding techniques. After anodising, the changes in surface chemistry and topography were evaluated by performing Field Emission Scanning Electron Microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Depending on the initial surface finish (ground and unground) and the anodising voltage, different interference colours were obtained on the anodised surfaces. At low anodising voltages, the surfaces displayed relatively compact structures whereas higher voltages resulted in the formation of porosity, cracks, and blisters in both conditions. These changes also influenced the corrosion behaviour. The samples which were ground prior to anodising exhibited higher resistance to corrosion compared to the unground samples.