Surface characteristics of anodic oxide films fabricated in acid and neutral electrolytes on Ti–10V–2Fe–3Al alloy

Abstract

Anodic oxide films were fabricated on Ti–10V–2Fe–3Al alloy in acid (H 2 SO 4 /H 3 PO 4 ) and neutral environmental friendly (C 4 H 4 O 6 Na 2 ) electrolytes. The morphology, roughness, crystalline structure of the anodic oxide film were characterized by using scanning electron microscopy, atomic force microscopy, Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The results showed that the oxide film fabricated in H 2 SO 4 /H 3 PO 4 electrolyte had a porous structure and the thickness of the film was 3.5 µm. The oxide film fabricated in C 4 H 4 O 6 Na 2 electrolyte presented a nonporous structure that sustained the evident microstructure of the substrate, and the thickness of the film was 6.0 µm. The surface average roughness values of the two types of films were 245 nm and 166 nm, respectively. The phase of the anodic oxide films consisted mainly of anatase and rutile. EIS results showed that the film fabricated in C 4 H 4 O 6 Na 2 electrolyte had higher impedance of the outer layer, while the film fabricated in H 2 SO 4 /H 3 PO 4 electrolyte had higher impedance of the inner layer. Moreover, we attempt to explain the differences in the anodizing kinetics, structure and electrochemical impedance of anodic oxide films by the different films growth processes in the two types of electrolytes. Copyright © 2012 John Wiley & Sons, Ltd.