Electrochemical formation of oxide films on Ti6Al4V alloy

Alexei Pilipenko

doi:10.21303/2585-6847.2018.00756

Abstract

The results of the study of the process of electrochemical oxidation of Ti6Al4V titanium alloy in solutions of tartaric, citric and oxalic acids are presented. It is shown that the nature of the forming dependencies of the alloy depends on the magnitude of the current density. When ja<0,5 A∙dm–2, a continuous oxide film does not form on the alloy surface and the specified voltage value is not reached. At ja>0,5 A∙dm–2, a continuous oxide film forms on the surface of the alloy and linear dependences are observed. Films produced under these conditions are interference colored. The maximum thickness of the film is determined by the specified value of the forming voltage U and does not depend on other parameters of electrolysis. For a number of identical values of U, the dependence of the limiting film thickness has a linear form. The color of the oxide film is determined by the voltage value and does not depend on the current density and electrolyte concentration. It is established that the color of the film corresponds to the magnitude of the forming voltage in the range of 10–100 V. The effect is due to the fact that film formation during anodic polarization occurs under the presence of a potential gradient, the magnitude of which is constant for titanium. An increase in a given value of U leads to a proportional increase in the limiting thickness of the oxide, which determines the color of its color. The research results to determine the effect of electrolysis parameters on the characteristics of oxide films make it possible to substantiate the regime for producing TiO2 films on the surface of the Ti6Al4V alloy. The obtained data are the basis for the development of technology for the electrochemical oxidation of titanium alloys to give their surface functional properties

Highlights

ELECTROCHEMICAL FORMATION OF OXIDE mixture of HNO3 and HF (3:1).Under normal conditions, the surface of titanium is covered with an oxide film, which causes its passivity [1]
The most informative for studying the anodizing process are the forming dependences U–τ, which allow to investigate the dynamics of film growth
Discussion of obtained results The forming dependencies (Fig. 1) show that an increase in ja contributes to an increase in the growth rate of the film. This observation corresponds to the Faraday law, for which the current density is the rate of electrochemical oxidation

Summary

Introduction

ELECTROCHEMICAL FORMATION OF OXIDE mixture of HNO3 and HF (3:1). The surface of titanium is covered with an oxide film, which causes its passivity [1]. The disadvantage of films is small thickness, which limits their use. Artificial films are used for surface modification of medical implants [2,3,4]. The electrolysis was carried out by setting the voltage on the cell in the range of 10–100 V with a step of 10 V using the Б5-49 power source. The signal of the end of the process was the operation of the power supply relay.

Methods

Results

Conclusion