Effect of Anodization Time on the Adhesion Strength of Titanium Nanotubes Obtained on the Surface of the Ti–6Al–4V Alloy by Anodic Oxidation

Abstract

In this work, titanium oxide nanotubes (TNTs) were formed by anodic oxidation on the surface of a Ti–6Al–4V alloy. An electrolyte based on ethylene glycol (EG) and ammonium fluoride (NH4F) was used. Different anodizing periods (10, 20, 30, 40, 50, and 60 min) with a constant potential of 60 V were established. The morphology of the TNT array was observed by scanning electron microscopy (SEM). The adhesion strength of the TNTs to the Ti–6Al–4V surface was evaluated using nanoscratch tests. The critical load of the different TNT layers was determined from the analysis of the groove of the nanoindenter path. It ranged from 0 mN for the samples exposed to 10 min of anodization to 47.0 ± 3.0 mN for samples exposed to 50 min. These results indicate the TNT layers formed at 50 min presented the best substrate adhesion among the specimen tested.