Effect of potential ramp in the potentiodynamic stage of anodization on morphology of nanostructured TiO2 developed on Ti6Al4V alloy

Abstract

Ti6Al4V titanium alloy samples, having disc shape of Ø16 x 3 mm, and an initial microrough morphology, were anodized in a custom built electrochemical cell having two electrode configuration, in 1M H3PO4 + 0.5 wt% HF electrolyte, anodization potential of 20 V, and anodization time of 30 min. The anodization potential was applied with different potential ramps (0.025, 0.05, 0.1, 0.2, 0.5, and 1 V/s). The modified surface morphology was evaluated using scanning electron microscopy (SEM). Our results show efficient synthesis of ordered nanotubular TiO2 layers on flat, microrough surfaces of two-phase Ti6Al4V alloy, and the importance of potential ramp parameter’s optimization. Potential ramps of 0.025, 0.05, and 0.1 V/s lead to development of continuous, uniform, self-ordered nanotubular TiO2 layers, with internal diameters in 25-110 nm range, and layer thickness in 150-400 nm range. Potential ramps of 0.2 and 0.5 V/s lead also to development of self-ordered nanotubular TiO2 layers, with internal diameters in 30-115 nm range, and layer thickness in 250-450 nm range, but the layers are discontinuous.