The Ti6Al4V alloy is already well-known likely material for implant applications. As well as pure titanium, Ti6Al4V alloy possess the ability to form spontaneously a thin passive oxide layer on the surface. This oxide layer provides an enhanced biocompatibility and may be optimum for the osseointegration if it is applied a tailoring of the surface topology and chemistry. The present paper addresses a study of Ti6Al4V surface modification by anodization as function of HF concentration in electrolyte and time, with the purpose to achieve an ordered porous titanium oxide layer. Prior to the anodization treatment the as-prepared surfaces were microstructurally characterized by SEM, EDX and XRD. The oxidized surfaces were subjected to SEM measurement in order to observe the achieved morphology

Annett GEBERT

Emanuela-Daniela STOICA

Fedor S. FEDOROV

Margitta UHLEMANN

Maria NICOLAE

The Annals of “Dunarea de Jos” University of Galati Fascicle IX Metallurgy and Materials Science

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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 1 – 2013, ISSN 1453 – 083X 
 
 
 
 
 
ANODIZATION TREATMENT OF Ti6Al4V  
IN ELECTROLYTES CONTAINING HF 
 
Emanuela-Daniela STOICA1,2, Fedor S. FEDOROV2,  
Maria NICOLAE1, Margitta UHLEMANN2, Annett GEBERT2 
1Materials Science and Engineering Faculty, Politehnica University of Bucharest, Romania,  
2IFW Dresden, Institute of Complex Materials 
email: stoicaemanueladaniela@yahoo.com 
 
ABSTRACT 
 
The Ti6Al4V alloy is already well-known likely material for implant 
applications. As well as pure titanium, Ti6Al4V alloy possess the ability to form 
spontaneously a thin passive oxide layer on the surface. This oxide layer provides 
an enhanced biocompatibility and may be optimum for the osseointegration if it is 
applied a tailoring of the surface topology and chemistry. The present paper 
addresses a study of Ti6Al4V surface modification by anodization as function of HF 
concentration in electrolyte and time, with the purpose to achieve an ordered 
porous titanium oxide layer. Prior to the anodization treatment the as-prepared 
surfaces were microstructurally characterized by SEM, EDX and XRD. The 
oxidized surfaces were subjected to SEM measurement in order to observe the 
achieved morphology. 
 
KEYWORDS: anodization, nanotube, nanopore, oxide, HF concentration 
 
1. Introduction 
 
Titanium and its alloys are the most used 
metallic materials for biomedical applications, due 
to their mechanical, biological and chemical 
properties. The α+β titanium alloys, such as 
Ti6Al4V and Ti6Al7Nb, are well-known metallic 
materials used for implant applications. Ti6Al4V 
possesses a good corrosion resistance and good 
physical properties even if there are some 
limitations regarding the mechanical properties 
(high Young’s modulus value) [1].  
Its biocompatibility is related to spontaneous 
formation of TiO2 thin adherent layer. This layer is 
specific to titanium and its alloys and beside TiO2 
contains also the alloying element oxides (Al and V 
are valve metals [2]) such as Al2O3 and V2O5. 
In recent years the surface modification 
techniques on “classical metallic biomaterials” 
showed a great interest for many researchers [3-4]. 
The anodization treatment is a new electrochemical 
method for surface modification [5]. Most of the 
anodization studies on Ti6Al4V were performed in 
electrolytes containing different amounts of NH4F 
[6-8], NaF [7] or HF [8].  
The present study is focused firstly on 
obtaining nanotubular oxide layers on Ti6Al4V 
substrate using the anodization technique in HF 
mixtures with H3PO4 and secondly, tno characterizing 
the achieved layers as function of electrolyte 
composition and anodization time. 
 
2. Experimental results 
 
2.1. Alloys characterization 
The cast alloy Ti6Al4V disks (2 mm thickness and 
11mm diameter) were microstructurally investigated 
before the anodization process. The samples were 
metallographically prepared and the polished surfaces 
were etched in a solution of 2% HF for a couple of 
seconds and subsequently analyzed using scanning 
electron microscopy (SEM) and energy dispersive X-ray 
analysis (EDX). Furthermore the samples were 
subjected to the x-ray diffraction analysis (XRD). 
The chemical composition of cast alloy samples 
was determined using inductively coupled plasma 
optical emission spectrometry analysis (ICP-OES). A 
very good agreement with the nominal composition was 
revealed. 
 
2.2. Anodization treatment 
Prior to the anodization treatment, the Ti6Al4V 
disks were ground with emery papers up to 2500, 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 1 – 2013, ISSN 1453 – 083X 
 
 
 
polished with 6µm diamond paste and cleaned by 
sonication in ethanol and distillated water. The 
electrochemical cell consisted of a two-electrode 
configuration with platinum foil as a counter 
electrode and Ti6Al4V sample as working 
electrode with a 0.28cm2 surface area exposed to 
the electrolyte. The anodization experiments were 
carried out using a high-voltage potentiostat 2400 
Source Meter Keithley connected to a digital 
multimeter (Keithley 2700 Multimeter /Data 
Acquisition System) interfaced to a computer. The 
electrolyte used for anodization treatment was a 
solution of 1 M H3PO4 with addition of 0.1 wt. % 
HF (E1) and 0.2 wt.%HF (E2) at room temperature. 
The anodization treatment comprised a potential 
ramp from open circuit potential (OCP) to 20V 
with a sweep rate of 20mV/s [6]. The potential of 
20V was held constant for 2400s, 3600s and 7200s 
in each electrolyte. After the anodization treatment 
all samples were rinsed in distilled water and dried. 
The structural and morphological 
characterization of the oxide layers was carried out 
with the Leo 1530 Scanning Electron Microscope 
(SEM). Moreover, the SEM analysis performed on 
nanotubular/nanoporous oxide layers allows us to 
measure the Dinner (inner diameter), Dtube (intertube 
distance), twall (wall thickness). The measurement 
error limit was around ± 5nm for Dinner, Dtube and 
around ±2 nm for twall. 
 
3. Results and discussions 
 
3.1. Alloys characterization prior 
anodization 
The microstructure characteristics are 
important aspects for further electrochemical 
response of an alloy.  
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 1. SEM images (BSE mode) of a Ti6Al4V 
sample cross section 
 
Hence, a detailed analysis of the Ti6Al4V 
substrates was conducted by means of SEM and XRD. 
Fig. 1 shows a SEM image in the composition of 
an HF etched cross-sectional area of a Ti6Al4V disk 
sample. The Ti6Al4V microstructure is clearly revealed 
with both phases α and β.  
The EDX measurement (Fig. 2) shows that α-
phase corresponds to the dark contrast areas and the β-
phase to the bright areas. The α-phase contains the Al 
element while the β-phase comprises the V element. 
The phase distribution is important for subsequent 
studies since, in electrolytes containing HF, the 
electrochemical behaviors of the α and β-phases may be 
different [6], [9]. 
The chemical composition of the investigated 
Ti6Al4V samples (as determined by ICP-OES) was 
89.19% Ti, 6.27% Al and 4.07% V. Thus, it is in very 
good agreement with the nominal composition. 
 
 
 
 
 
 
 
 
Fig. 2. EDX images of a Ti6Al4V sample  
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 3. XRD pattern of Ti6Al4V sample 
 
The alloys XRD patterns (Fig.3) have shown that 
the main intensity diffraction peaks correspond to the α-
phase, since this phase is the major one. The main β-
phase reflections were recorded around 2θ=76.8°and 
2θ=77.8°. 
 
3.2. Characterization of the anodized  
alloys surface 
Scanning electron microscopy was employed for 
the structural and morphological characterization of the 
Ti6Al4V sample surfaces after the anodization process.  
 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 1 – 2013, ISSN 1453 – 083X 
 
 
 
The anodization treatment in both electrolytes 
for 2400s and 7200s has shown only etched 
surfaces.  
Thus, it can be assumed that the HF 
concentration of electrolytes is less important since 
for more and less than 3600 s the result was the 
same. This phenomenon is attributed to the last 
stages in the mechanism of TiO2 growth [12-14]. 
The HR-SEM image of the alloy surface anodized 
in E1, for 3600s (Fig.4) shows that the alloy phases 
are differently affected by the treatment in fluoride-
containing solution. Under these conditions on α-
phase region a nanotubular oxide structure (Fig. 5) 
had formed, while on the β-phase region only a 
porous oxide structure was observed. In literature, 
it was found similar behavior of the α and β regions 
on Ti6Al4V anodized surface even the electrolytes 
were NH4F [6], or HF [8] solutions.  
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 4. Ti6Al4V HR-SEM image of α surface 
anodized in E1, for 3600s 
 
The Dinner of the tubes growth on α-region 
was around 70nm while the Dtube and twall were 
around 90nm and 20nm, respectively. Moreover, 
the nanopores Dinner growth on β-region could be 
measured and the value was around 60nm. 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 5. Ti6Al4V HR-SEM image of α+β 
surface anodized in E1, for 3600s 
The nanopores Dinner is smaller than the nanotubes 
one, this aspect may be typical for Ti6Al4V anodized 
surface [6]. It should be mentioned that this method has 
certain limitations regarding measurement accuracy, 
and, for this reason an error limit of 5nm was taken. 
For the second electrolyte E2, with higher HF 
concentration, for 3600s polarization a porous structure 
was achieved for both α and β regions (Fig. 6). 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 6. Ti6Al4V SEM image of α+β surface 
anodized in E2, for 3600s 
 
The α-regions have shown a much ordered 
nanoporous structure (Fig.7). This aspect was also 
found in literature [6] for α-phase region. The nanopores 
Dinner was found around 60nm (±5nm). 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 7. Ti6Al4V HR-SEM image of α+β surface 
anodized in E2, for 3600s 
 
The behavior of the phases of the α+β titanium 
alloys is different depending of the β stabilizer element.  
Thus, even if Ti6Al7Nb is also an α+β titanium 
alloys, in literature it was found that anodization in HF 
electrolyte contain led to upper ordered nanoporous 
layer growth on β-region [9].  
 
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FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 1 – 2013, ISSN 1453 – 083X 
 
 
 
4. Conclusions 
 
The investigations regarding the anodization 
behavior of the α+β Ti6Al4V alloy were conducted 
in H3PO 4/ 0.1 wt% HF (E1) and 0.2 wt% HF (E2) 
electrolytes applying a potential of 20V for up to 
7200s potential and then sweeping the potential 
with 20mV/s. Nanotubular oxide structures were 
obtained and it was demonstrated that the optimum 
polarization time is 3600s for an 0.1wt% HF 
concentration (E1). The Dinner of the oxide 
nanotubes were about 70nm. while the β-phase 
regions showed only a random disordered 
nanoporous structure. Furthermore, at 2400s and 
7200s anodization time no nanotubular or 
nanoporous layers were observed.  
It can be concluded that employing the 
presented anodization parameters a nanotubular 
oxide structure was observed already after 3600s in 
electrolyte with less HF concentration. 
 
Acknowledgment 
The work has been funded by the Sectoral 
Operational Programme Human Resources 
Development 2007-2013 of the Romanian Ministry 
of Labour, Family and Social Protection through 
the Financial Agreement POSDRU/88/1.5/S/61178. 
 
References 
 
 [1]. D. M. Brunette, P. Tengvall, M. Textor, P. Thomsen - 
Titanium in Medicine: Material Science, Surface Science, 
Engineering, Biological Responses and Medical Applications, 
1st edition Springer; Berlin, (2001), pp.14-19. 
 [2]. M.M. Lohrengel - Thin anodic oxide layers on aluminium  
and other valve metals: high field regime, Materials Science and 
Engineering, Vol. R11, pp.243-294, (1993). 
 [3]. X. Liu, P. Chu, C. Ding - Surface modification of titanium, 
titanium alloys, and related materials for biomedical applications, 
Materials Science and Engineering: Reports: Vol. R47, pp.49-121, 
(2004). 
 [4]. K. Subramani - Titanium Surface Modification Techniques for 
Implant Fabrication – From Microscale to the Nanoscale, Journal of 
Biomimetics, Biomaterials, and Tissue Engineering. Vol. 5, pp.39-56, 
(2010). 
 [5]. V. Zwilling, E. Darquel Ceretti - Structure and 
physicochemistry of anodic oxide films on titanium and TA6V alloy, 
Surface and Interface Analysis, Vol.27, pp. 629-637, (1999). 
 [6]. J.M. Macak, H. Tsuchiya, L. Taveira, A. Ghicov, P. Schmuki 
- Self-organized nanotubular oxide layers on Ti-6Al-7Nb and Ti-6Al-
4V formed by anodization in NH4F solutions, Journal of Biomedical 
Materials Research. Part A, Vol. 75, pp. 928-33, (2005). 
 [7]. E. Matykina, a. Conde, J. de Damborenea, D.M.Y. Marero, 
M. a. Arenas - Growth of TiO2-based nanotubes on Ti–6Al–4V alloy, 
Electrochimica Acta, Vol.56, pp.9209-9218, 2011. 
 [8]. H. Lukáčová, B. Plešingerová, M. Vojtko, G. Bán - 
Electrochemical treatment of Ti6Al4V (1. Part) - Acta Metallurgica 
Slovaca, Vol.16, pp. 186-193, (2010).  
 [9]. H.-C. Choe - Nanotubular surface and morphology of Ti-binary 
and Ti-ternary alloys for biocompatibility, Thin Solid Films, Vol.519, 
pp.4652-4657, (2011). 
[10]. E. Matykina, J.M. Hernandez-López, A. Conde, C. Domingo, 
J.J. de Damborenea, M. A. Arenas - Morphologies of 
nanostructured TiO2 doped with F on Ti–6Al–4V alloy, 
Electrochimica Acta, Vol.56, pp.2221-2229, (2011). 
[11]. A. Kaczmarek, T. Klekiel, E. Krasicka-Cydzik - Fluoride 
concentration effect on the anodic growth of self-aligned oxide 
nanotube array on Ti6Al7Nb alloy, Surface and Interface Analysis, 
Vol.42, pp.510-514, (2010). 
[12]. G. Crawford, N. Chawla - Porous hierarchical TiO2 
nanostructures: Processing and microstructure relationships, Acta 
Materialia, Vol.57, pp. 854-867, (2009). 
[13]. S.E. Pust, D. Scharnweber, C. Nunes Kirchner, G. Wittstock 
- Heterogeneous Distribution of Reactivity on Metallic Biomaterials: 
Scanning Probe Microscopy Studies of the Biphasic Ti Alloy Ti6Al4V, 
Advanced Materials, Vol.19, pp.878-882, (2007). 
[14]. P. Roy, S. Berger, P. Schmuki - TiO2 nanotubes: synthesis and 
applications, Angewandte Chemie (International Ed. in English), Vol. 
50, pp.2904-39, (2011). 
 
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Anodization Treatment of Ti6Al4V in Electrolytes Containing HF

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Anodization Treatment of Ti6Al4V in Electrolytes Containing HF

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