• International Journal of Technology (IJTech)
  • Vol 14, No 4 (2023)

Surface Coating Effect on Corrosion Resistance of Titanium Alloy Bone Implants by Anodizing Method

Surface Coating Effect on Corrosion Resistance of Titanium Alloy Bone Implants by Anodizing Method

Title: Surface Coating Effect on Corrosion Resistance of Titanium Alloy Bone Implants by Anodizing Method
Eva Oktavia Ningrum, Ianatul Khoiroh, Hanifah Inas Nastiti, Ryan Anindya Affan, Achmad Dwitama Karisma, Elly Agustiani, Agus Surono, Heri Suroto, S. Suprapto, Lulu Sekar Taji, Sinung Widiyanto

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Cite this article as:
Ningrum, E.O., Khoiroh, I., Nastiti, H.I., Affan, R.A., Karisma, A.D., Agustiani, E., Surono, A., Suroto, H., Suprapto, S., Taji, L.S., Widiyanto, S., 2023. Surface Coating Effect on Corrosion Resistance of Titanium Alloy Bone Implants by Anodizing Method. International Journal of Technology. Volume 14(4), pp. 749-760

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Eva Oktavia Ningrum Department of Industrial Chemical Engineering, Faculty of Vocational Studies, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia
Ianatul Khoiroh Department of Chemical & Environmental Engineering, Faculty of Science and Engineering, University of Nottingham Malaysia, Jalan Broga 43500 Semenyih, Selangor, Malaysia
Hanifah Inas Nastiti Department of Industrial Chemical Engineering, Faculty of Vocational Studies, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia
Ryan Anindya Affan Department of Industrial Chemical Engineering, Faculty of Vocational Studies, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia
Achmad Dwitama Karisma Department of Industrial Chemical Engineering, Faculty of Vocational Studies, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia
Elly Agustiani Department of Industrial Chemical Engineering, Faculty of Vocational Studies, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia
Agus Surono Department of Industrial Chemical Engineering, Faculty of Vocational Studies, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia
Heri Suroto Orthopedic and Traumatology Department, Faculty of Medicine, Airlangga University/Dr. Soetomo General Academic Hospital, Jl. Mayjen Prof. Dr. Moestopo No.47, Surabaya, Jawa Timur 60132, Indonesia
S. Suprapto Department of Industrial Chemical Engineering, Faculty of Vocational Studies, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia
Lulu Sekar Taji Department of Industrial Chemical Engineering, Faculty of Vocational Studies, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia
Sinung Widiyanto Magister of Ocean Engineering, Faculty of Engineering and Marine Sciences, Hang Tuah University, Jl. Arief Rahman Hakim No.150, Keputih, Kec. Sukolilo, Surabaya 60111, Indonesi
Email to Corresponding Author

Abstract
Surface Coating Effect on Corrosion Resistance of Titanium Alloy Bone Implants by Anodizing Method

In the presented work, the formation of anodic oxide film on Ti-6Al-4V ELI (Extra Low Interstitial) alloy in 0.02 M trisodium phosphate (Na3PO4) electrolyte solution using various voltages were investigated. The color produced by the anodizing, the intensity of TiO2 content, the thickness of the oxide layer, and the corrosion rate were examined. It was obtained that the color appearance of Ti-6Al-4V ELI could be changed easily by altering the applied voltages. The higher the voltage applied in the anodizing process, the thicker the titanium oxide layer formed. The corrosion resistance analysis in a Simulated Body Fluid revealed that the non-anodized specimen showed a higher corrosion rate compared to the anodized specimen. The increase of oxide layer thickness leads to a significant decrease in corrosion rate and consequently increases the corrosion resistance. In addition, the anodized sample achieved the highest corrosion resistance at 15 V.

Anodizing; Corrosion resistance; Titanium oxide; Ti-6Al-4V alloy

Introduction

A bone implant is a medical device used to strengthen the existing bone structure or supports an injured bone structure. In this case, approximately 90% of implants in Indonesia imports. Therefore, given the rising demand for implants, the development of bone implants is a crucial debate issue. Based on the biomedical viewpoint, implant stability and the osseointegration process, which has the potential for rehabilitation, are the most important internal factors in the implantation of medical devices. Therefore, it is essential to create bone implants that have high-quality and effective when placed within the body (Dewi et al., 2020; Genisa et al., 2020; Izmin et al., 2020). Orthopedic implants are now made from various materials, including polymers, ceramics, metals, and composites. The majority of metals are bio tolerant, although titanium and its alloys have a bioinert nature under specific circumstances (Koju, Niraula and Fotovvati, 2022).
       Titanium Ti-6Al-4V ELI is a commonly used implant material in the medical field due to its mechanical and corrosion resistance properties  (Szymczyk-Ziolkowska et al., 2022; Jaafar et al., 2020; Atmani et al., 2018; Karambakhsh et al., 2011). This corrosion resistance property emerges due to the formation of a natural oxide layer, which mainly contains TiO2 on the titanium surface when it contacts the air (Lestari et al., 2020). In addition, the Ti-6Al-4V ELI alloy material is the most commonly used material for implants in orthopedics (Kashyap, Rashid, and Khanna, 2022; Swain et al., 2021; Szymczyk-Ziolkowska et al., 2021; Gabor et al., 2020; Kiel-Jamrozik et al., 2015). Furthermore, to its advantages, this material has several weaknesses, including the thin natural oxide layer on titanium causing implant wornness, low bone bonding capacity, and incapability to prevent metal ions exposure due to implant degradation. Besides, titanium alloys also have poor osseointegration in long-term implantation (Lestari et al., 2020).
      Implant surface modification is necessary to obtain good implant properties and performance for the body. This surface modification is important to increase surface energy by providing surface roughness and chemical composition. This will increase tissue adhesion and implant integration as well as reduce bacterial reactions and inflammatory responses in the body (Rani and Jatolia, 2018). In this case, one of the methods that can be employed to improve implant performance is an anodizing method. Anodizing method is metal oxidation carried out in certain electrolytes by producing an electric field at the metal/electrolyte interface (Izmir and Ercan, 2019). This method is the easiest method to modify the thickness, composition, and morphology of the metal oxide layer. Moreover, the anodization process is used to restrict the infiltration process (Kiel-Jamrozik et al., 2015). A thin oxide layer grows on the implant’s surface during this process. Properties of the layer depend on the electrolyte, production method, oxidation time, and electric parameters of the process (Kiel-Jamrozik et al., 2015; Szewczenko et al., 2015; Ziebowicz, Ziebowicz and Baczkowski, 2015; Al-Mobarak and Al-Swayih, 2014; Indira, Mudali and Rajendran, 2013; Fadl-allah, Quahtany and El-Shenawy, 2013; Bhola et al., 2011; Szewczenko et al., 2010; Narayanan and Seshadri, 2007; Nagy et al., 2005; Van-Gils et al., 2004; Roessler et al., 2002).
       According to prior research, some inorganic ions, such as molybdate and metavanadate, can passivate titanium in solutions of sulfuric and hydrochloric acids (Mogoda, Ahmad, and Badawy, 2004). Anodizing has also been performed in phosphoric acid solutions under different conditions to improve the corrosion resistance of Ti6Al4V alloy in the simulated physiological environment such as (Karambakhsh, Afshar, and Malekinejad, 2012) conducted anodizing on the Ti-6Al-4V alloy in phosphoric acid electrolyte and evaluated its corrosion resistance in 3 different solutions (Ringer's solution, artificial saliva solution, and a mixture of Ringer's solution + H2O2). The research further resulted that the higher the voltages, the higher the corrosion resistance obtained due to the passivity produced by the anodizing process. Furthermore, Martinez, Flamini, and Saidman (2022) studied the impact of inhibitor anions on the alloy corroded in Ringer solution. In this case, galvanostatic anodization of Ti–6Al–4V alloy with inorganic inhibitors such as Na2MoO4, NaH2PO4, and NH4VO3 solutions produced colorful thin oxide layers. Their findings demonstrated that, regardless of the solution employed, compact, amorphous oxides free of pores or fractures may be produced. The alloy anodized in Na2MoO4 solution had the lowest corrosion current density. In addition, no signs of corrosion or fractures were seen (Martinez, Flamini and Saidman, 2022).
      (Tamilselvi, Raman and Rajendran, 2006) also evaluated the corrosion of Ti-6Al-4V ELI alloy using the electrochemical impedance spectroscopy method in a Simulated Body Fluid (SBF) solution. This solution was used to simulate the physiological conditions in the body. In addition, to develop the color chart of the Ti-6Al-4V alloy, anodizing was also carried out in trisodium phosphate electrolyte (Wadhwani et al., 2018).
     Research concerning the anodizing process of Ti-6Al-4V alloy has been numerously conducted; however, it is only limited to the use of corrosion resistance test solution, causing its inability to simulate the body's physiological condition. Therefore, the current research used SBF solution. The effect of various voltage on the implant color visual, the mass of the oxide layer formed, oxide film thickness, and implant corrosion resistance were investigated in this study. Moreover, the correlation between film thickness and its corrosion resistance was also elucidated. In addition, the trisodium phosphate electrolyte solution was chosen because it provides better corrosion resistance compared to the acidic electrolyte solution (Karambakhsh et al., 2015).

Experimental Methods

2.1. Materials
      The main material used in this research was Ti-6Al-4V ELI metals act as an anode that would be layered by TiO2 using an anodizing method. An aluminum foil sheet was also used as a cathode. The electrolyte used was 2 g of trisodium phosphate dodecahydrate purchased from Merck, which initially dissolved in 1000 mL aquadest. Titanium wire 28 AWG 0.3 mm and alligator clip were also employed as the supporter of both Ti-6Al-4V ELI metal and aluminum foil during the anodizing process. The electrical power source was obtained from DC Power Supply WANPTEK of NPS 1203W 120V/3A type. In addition, a SBF solution was used as an electrolyte during the potentiodynamic polarization analysis to investigate the corrosion rate of anodized Ti-6Al-4V ELI metal material.

2.2. Methods
      Anodizing method was done in Na3PO4 (base solution) electrolyte solution. In this case, the Ti-6Al-4V specimen obtained pre-treatment to make the implant surface shiny so that the anodizing color produced can be seen clearly. This pre-treatment process used Ti-6Al-4V ELI metals, previously polished using langsol or green stone to obtain a mirror-like surface. The solution used for anodizing was Trisodium Phosphate solution with a concentration of 0.02 M of 250 mL volume. The cathode was aluminum foil, and the anode was the Ti-6Al-4V specimens. Anodizing process was performed within 30 s for each sample, the variable parameter being the anodizing voltage. Anodizing was performed in the 15-75 V voltage range, and with the steps of 15 V. The schematic apparatus for an anodizing process is shown in Figure 1.


      
   Figure 1 Anodizing experiment setup

2.2.1. XRD Analysis
        XRD was used to identify the titanium oxide crystal component formed after anodizing.

2.2.2. Spectrophotometry Analysis
    Spectrophotometry Analysis was carried out to determine the quantitative parameters of the specimen surface color (Konica Minolta CM-5 spectrophotometer). In order to measure the color difference of each specimen, this tool would obtain data values of L*, a*, and b*, where chromaticity was obtained using the CIELAB color space method based by using Equation (1)

   
The wavelength formed from each color can be obtained through the visible light spectrum. The refractive index value was calculated using Equation (2) to determine the thickness of the oxide layer formed.

2.2.3. Potentiodynamic Polarization Analysis
      This analysis was done to investigate the corrosion behavior of the titanium specimen without and after anodizing. Potentiodynamic polarization involved the CorrTest tool equipped with CS Studio 5 software. This tool series consists of three electrodes; those are: the referral electrode (SCE, Saturated Calomel Electrode), the working electrode (titanium specimen), and the assistant electrode (Graphite). In addition, an SBF solution at a pH of 7.4 was employed to investigate the titanium corrosion behavior (Tamilselvi, Raman and Rajendran, 2006). In this case, the pH of human blood was in the range of 7.35-7.45 (Bakr et al., 2021). The following table further lists the composition of the SBF solution.
Table 1 SBF Solution Composition

No

Reagent

Composition (g/L)

1.

NaCl

8.00

2.

KCl

0.40

3.

CaCl2

0.18

4.

NaHCO3

0.35

5.

Na2HPO4.2H2O

0.48

6.

MgCl2.6H2O

0.10

7.

KH2PO4

0.06

8.

MgSO4.7H2O

0.10

9.

Glucose

1.00


Results and Discussion

3.1. Analysis of Anodizing Results in Trisodium Phosphate Electrolyte

3.1.1. Effect of Voltage on the Implant Color Visual
       During the anodizing process, each voltage results in a different color. This interference color is caused by stoichiometric defects in oxide layer composition or wave interference on the crystal layer (Kahar et al., 2020). Based on the anodizing process, it was obtained that goldish brown, dark blue, light blue, yellow, and goldish yellow colors were produced from a voltage of 15, 30, 45, 60, and 75 V, respectively, shown in Figure 2.