Electrochemical Behaviour of Ti and Ti-6Al-4V Alloy in Phosphate Buffered Saline Solution.

Senka Gudić,Aleš Nagode,Dario Kvrgić,Ladislav Vrsalović

doi:10.3390/ma14247495

Abstract

The electrochemical behavior of commercially pure titanium (CP Ti) and Ti-6Al-4V (Grade 5) alloy in phosphate buffered saline solution (PBS, pH = 7.4) at 37 °C (i.e., in simulated physiological solution in the human body) was examined using open circuit potential measurements, linear and potentiodynamic polarization and electrochemical impedance spectroscopy methods. After the impedance measurements and after potentiodynamic polarization measurements, the surface of the samples was investigated by scanning electron microscopy, while the elemental composition of oxide film on the surface of each sample was determined by EDS analysis. The electrochemical and corrosion behavior of CP Ti and Ti-6Al-4V alloys is due to forming a two-layer model of surface oxide film, consisting of a thin barrier-type inner layer and a porous outer layer. The inner barrier layer mainly prevents corrosion of CP Ti and Ti-6Al-4V alloy, whose thickness and resistance increase sharply in the first few days of exposure to PBS solution. With longer exposure times to the PBS solution, the structure of the barrier layer subsequently settles, and its resistance increases further. Compared to Ti-6Al-4V alloy, CP Ti shows greater corrosion stability.

Highlights

Titanium and its alloys possess excellent properties such as low density, good formability, high specific strength and corrosion resistance, weldability and biocompatibility, making them desirable materials, which finds applications in different important areas such as automobile, aerospace, chemical and petrochemical industry, military and medicine [1,2,3,4,5].Titanium and its alloys are the primary materials for biomedical and dental implant applications
In Hank’s solution, electrochemical measurements at 25 ◦ C indicate higher corrosion resistance of Ti-6Al-4V alloys compared with pure titanium, which was explained by the beneficial influence of Al and V alloying elements, which reduces the dissolution rate of the passive layer formed in the solution
The initial increase in barrier layer resistance was explained in terms of the oxide film growth, while a slight decrease is a consequence of the chloride ion attack [28]

Summary

Introduction

Titanium and its alloys possess excellent properties such as low density, good formability, high specific strength and corrosion resistance, weldability and biocompatibility, making them desirable materials, which finds applications in different important areas such as automobile, aerospace, chemical and petrochemical industry, military and medicine [1,2,3,4,5].Titanium and its alloys are the primary materials for biomedical and dental implant applications. In the case of Ti-6Al-4V alloy, the presence of low contents of aluminium and vanadium oxides (Al2 O3 and V2 O5 ) in the porous layer of the passive film, have been detected [17,18,19]. These oxides can dissolve and deteriorate the passivity of Ti-6Al-4V alloy. The same investigations on 37 ◦ C have shown that the passive films have lower resistance on Ti-6Al-4V than that of titanium due to local corrosion processes accelerated by the presence of chloride ions

Methods

Results

Conclusion