Alloy In Simulated Body Fluid Research Articles

Electrochemical polymerization of pyrrole over AZ31 Mg alloy for biomedical applications

Electrochemical polymerization of pyrrole (Py) from aqueous salicylate solution over AZ31 Mg alloy was carried out using cyclic voltammetry (CV). The effect of monomer concentration on the surface and electrochemical corrosion in simulated body fluid (SBF) were analysed. Attenuated total reflection-infrared (ATR-IR) spectra showed the characteristic ring stretching peaks for polypyrrole (PPy). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies exhibited typical cauliflower morphology with rough surface for PPy coated AZ31 Mg alloy. Open circuit potential measurement and potentiodynamic polarization studies revealed that the coating prepared using 0.25M of Py had positive shift of about 120mV in corrosion potential and lower corrosion current density (0.03mA/cm2) compared to other concentrations and uncoated AZ31 Mg alloy (0.25mA/cm2). Electrochemical impedance spectroscopic (EIS) studies of uncoated and PPy coated Mg alloy in SBF revealed three-time constants behaviour with about one order of increment in impedance value for 0.25M of Py.

Surface analysis and corrosion resistance of a new titanium base alloy in simulated body fluids

A new quaternary Ti–20Nb–10Zr–5Ta alloy with β-near microstructure was obtained. Its native passive film composition and its modification and corrosion resistance after 2000 immersion hours in simulated biofluids were studied. The native film on the alloy surface contains TiO2, Nb2O5, ZrO2, Ta2O5 protective oxides as was demonstrated by XPS. After 2000h, XPS revealed the presence of same oxides and calcium, phosphorous ions deposited from physiological solutions as hydroxyapatite. In Ringer and Ringer–Brown solutions, the new alloy presented low corrosion rates. Impedance data exhibited a passive film with two layers: an inner, barrier layer and an outer, porous layer.

Effect of oxidation time on the corrosion behavior of micro-arc oxidation produced AZ31 magnesium alloys in simulated body fluid

The electrochemical corrosion behavior of microarc oxidation (MAO) coatings produced at various oxidation times on AZ31 Mg alloys was studied in a simulated body fluid (SBF). The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to characterize the corrosion behavior. The influences of the MAO time on the microstructure and corrosion properties are discussed. The initial porosity of the MAO coating was evaluated by the potentiodynamic polarization method. Post-corrosion phase identification showed that hydroxyapatite (HA) was formed on the surface of the samples. The ratio of Ca/P in HA was determined by the X-ray Fluorescence (XRF) technique. A physical model of the corrosion process with equivalent circuits at different corrosion stages is proposed.

Corrosion of Biodegradable Implant Mg-2Ca-xZn Alloy in Simulated Body Fluid with the Addition of Zn

The affect of adding of Zn on the microstructure and corrosion properties was investigated in this work. Vacuum induce melting was used to obtain the Mg-2Ca-xZn (wt.%) (x = 0%, 1%, 2% and 3%) alloys. Erode test was carried out in the Hank’s simulated body fluid for the alloys and the increasing of weight is carefully measured. The microstructure of the alloys was observed with optical microscope and SEM. It is found that and the Mg-2Ca-1Zn alloy is with the best corrosion resistance. Hardness increases as the adding of Zn in the alloys.

On corrosion behaviour of magnesium alloy AZ31 in simulated body fluids and influence of ionic liquid pretreatments

This paper reports on the corrosion of Mg alloy AZ31 in simulated body fluid (SBF) using static immersion tests and electrochemical impedance spectroscopy. A preliminary study on the effect of flowing SBF on the corrosion behaviour of AZ31 has also been carried out. Low toxicity ionic liquids (ILs) trimethyl(butyl)phosphonium diphenyl phosphate P1444DPP and trihexyl(tetradecyl)phosphonium bis-2,4,4trimethylpentyl-phosphinate [P66614][i(C8)2PO2] have been used to provide corrosion protection for AZ31 in SBF. Time dependent immersion tests indicate that under static conditions, AZ31 suffers severe localised corrosion in SBF, with pits developing predominantly beside the Al–Mn intermetallic phase in the α matrix. At longer immersion times, the corrosion product eventually precipitates and covers the entire specimen surface. When exposed to SBF under flowing conditions with a shear stress of 0·88 Pa, more uniform corrosion was observed. The optical profilometry results and electrochemical impedance spectroscopy analysis suggest that both P1444DPP and [P66614][i(C8)2PO2] pretreatments can increase the corrosion resistance of AZ31 in SBF, in particular by decreasing the number of deeper pits found on the alloy surface. Cytotoxic test shows that the presence of the ILs P1444DPP and [P66614][i(C8)2PO2] in cell culture media slightly inhibits the growth of human coronary artery endothelial cells in comparison with the good cell viability around the treated specimen. A pretreatment with IL is used in order to improve the corrosion resistance of this alloy in SBF.

Study of the biotribocorrosion behaviour of titanium biomedical alloys in simulated body fluids by electrochemical techniques

The corrosion and wear behaviour of wrought titanium alloys (Ti-Grade 2, Ti6Al4V and Ti6Al4V-ELI) immersed in phosphate buffered solution (PBS) and phosphate buffered solution with bovine serum albumin (PBS+BSA) has been analysed by electrochemical techniques and surface microscopy. The influence of the alloy composition and microstructure on the tribo- electrochemical behaviour was analysed by potentiodynamic studies and potentiostatic tests (applied electrochemical potentials) under sliding conditions. Plastic deformation and third bodies were observed at the end of the tests by optical, confocal and scanning electron microscopy (SEM). Although the degradation mechanism was the same in all the studied alloys, wear debris was found to be material and solution chemistry dependent. α+β phase Ti6Al4V alloy shows lower wear damage than the α phase Ti-Grade 2 alloy. Main effect of chemical composition and microstructure of the alloy was found in the wear accelerated corrosion, which is twice in the case of the Ti-Grade 2. Effect of the repassivation time and passive film growth on the wear behaviour of the Ti6Al4V-ELI was also analysed by carrying out intermittent tests. Wear coefficient increases when rest time between sliding cycles increases due to the growth of the passive films during the pause periods. BSA adsorbs on the metallic surface thus reducing the repassivation kinetics and therefore hindering the effect of pause periods during sliding.

Plasma enhanced chemical vapor deposited silicon coatings on Mg alloy for biomedical application

Amorphous Si film was prepared by plasma enhanced chemical vapor deposition (PECVD) of SiH4 on WE43 alloy for biomedical application. The microstructure and the composition of the film were investigated by glancing angle X-ray diffraction (GAXRD), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. The immersion test indicated that Si film could efficiently slow down the degradation rate of WE43 alloy in simulated body fluid (SBF) at 37±1°C. MTT assay suggested that the extract of the Si coated WE43 alloys was harmless to murine fibroblast cells (L 929). Hemolysis test and blood platelets adhesion test were conducted, and the results show that the hemolysis of WE43 alloy decreased after being coated by Si and the platelets attached on the Si film were at the inactivated stage with a round shape.

Using Biocompatible Ionic liquid to Control the Corrosion of Mg Alloys in Simulated Body Fluid

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Effect of Alloying Elements on Corrosion Behavior of Zr-Based Binary Alloys in Simulated Body Fluid

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Microstructure and Corrosion Resistance of Al<sub>2</sub>O<sub>3</sub>-ZrO<sub>2</sub> Composite Coating on Biomedical Magnesium Alloy Fabricated by Cathodic Plasma Electrolytic Oxidation

A relatively new method called cathodic plasma electrolytic oxidation (CPEO) was development to fabricate Al2O3–ZrO2 composite coating on AZ91 biomedical magnesium alloy. The microstructure and properties of the composite coating including phase composition, surface and cross section morphology, thickness and bonding strength were investigated. The corrosion behavior of the coated magnesium alloy in simulated body fluids(SBF) was primarily evaluated. The results showed that the coating was composed of c-ZrO2, α-Al2O3 and γ-Al2O3. The coating surface was coarse and porous with the average pores diameters of 5 µm. The thickness of the coating was about 60 µm and the bonding strength of coating to the AZ91 substrate was 22 MPa. The polarization test indicated that corrosion potential (Ecorr) and corrosion current density (icorr) of the coated samples in SBF were −1.56V and 8.89×10-7 A/cm2 , respectively, whose corrosion resistance was significantly improved compared to the uncoated sample.

Improved surface corrosion resistance of WE43 magnesium alloy by dual titanium and oxygen ion implantation

Magnesium alloys are potential biodegradable materials and have attracted much attention due to their outstanding biological performance and mechanical properties. However, their rapid degradation inside the human body cannot meet clinical needs. In order to improve the corrosion resistance, dual titanium and oxygen ion implantation is performed to modify the surface of the WE43 magnesium alloy. X-ray photoelectron spectroscopy is used to characterize the microstructures in the near surface layer and electrochemical impedance spectroscopy, potentiodynamic polarization, and immersion tests are employed to investigate the corrosion resistance of the implanted alloys in simulated body fluids. The results indicate that dual titanium and oxygen ion implantation produces a TiO2-containing surface film which significantly enhances the corrosion resistance of WE43 magnesium alloy. Our data suggest a simple and practical means to improve the corrosion resistance of degradable magnesium alloys.

The Y-doped MgZnCa alloys with ultrahigh specific strength and good corrosion resistance in simulated body fluid

The microalloying effects of Y on the microstructure, mechanical properties and bio-corrosion resistances of Mg69Zn27Ca4 (at.%) alloy were investigated by X-ray diffraction, compressive tests and electrochemical treatments, respectively. The Y-bearing Mg–Zn–Ca alloys were found to possess an ultrahigh compressive strength above 1000MPa as well as high specific strength of 3.44×105Nmkg−1. The enhanced mechanical properties can be attributed to the ductile dendrite phase, Mg12YZn, which is dispersed in the matrix with the Y addition. Furthermore, the Y-doped Mg–Zn–Ca alloys studied in this work have much better corrosion resistance than traditional ZK60 and pure Mg alloys in simulated body fluid (SBF) at 37°C, which could be good candidates to be used as biomedical materials.

Controlled degradation of a magnesium alloy in simulated body fluid using hydrofluoric acid treatment followed by polyacrylonitrile coating

This paper describes the protection mechanism of polyacrylonitrile coatings on a hydrofluoric acid treated magnesium alloy. The protective performance of the adopted methodology was investigated by electrochemical impedance spectroscopy and immersion tests in 3.5wt.% NaCl and in simulated body fluid (SBF). It was observed that interfacial reactions and interactions between polymer and substrate rendered long-term protection for the metal. A detailed characterization of the coating properties and of the interfacial processes is provided and the potential of the adopted methodology for biomedical application is discussed.

Biocorrosion of Biodegradable Implant Mg-xCa-4Zn Alloy in Simulated Body Fluid with the Addition of Ca

The effect of Ca on the microstructure and corrosion properties was investigated. Vacuum induce melting was used to obtain the Mg-xCa-4Zn (wt.%) (x = 0%, 1%, 2% and 3%) alloys. Erode test was carried out in the Hank’s simulated body fluid for the alloys and the increasing of weight is carefully measured. The microstructure of the alloys was observed with optical microscope and energy spectrum analysis was used for accurate composition. It is found that as the increasing of Ca, the corrosion extent is getting serious for the Mg-xCa-4Zn alloys. Hardness increases as the adding of Ca in the alloys.

Electrochemical behavior of biocompatible AZ31 magnesium alloy in simulated body fluid

Dense oxidation coatings have been successfully developed on biocompatible AZ31 magnesium alloy, using microarc oxidation technique, to improve the corrosion resistance. Three different deposition voltages of 250, 300, and 350 V have been employed. The effect of voltage on the coating corrosion resistance has been evaluated through electrochemical experiments in a simulated body fluid (SBF) up to 7 days. Potentiodynamic polarization and electrochemical impedance spectroscopy scans were performed in the SBF solution, followed by optical microscopy surface inspection. The results indicate that the corrosion rates of the coatings are in the order of 250 300 > 350 V. Both the electrochemical tests and the surface inspection suggest that the 250 V coating has the highest corrosion resistance, with lowest corrosion current density, highest Rct, and the best surface quality.

Corrosion mechanism and model of pulsed DC microarc oxidation treated AZ31 alloy in simulated body fluid

This paper addresses the effect of pulse frequency on the corrosion behavior of microarc oxidation (MAO) coatings on AZ31 Mg alloys in simulated body fluid (SBF). The MAO coatings were deposited by a pulsed DC mode at four different pulse frequencies of 300Hz, 500Hz, 1000Hz and 3000Hz with a constant pulse ratio. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used for corrosion rate and electrochemical impedance evaluation. The corroded surfaces were examined by X-ray diffraction (XRD), X-ray fluorescence (XRF) and optical microscopy. All the results exhibited that the corrosion resistance of MAO coating produced at 3000Hz is superior among the four frequencies used. The XRD spectra showed that the corrosion products contain hydroxyapatite, brucite and quintinite. A model for corrosion mechanism and corrosion process of the MAO coating on AZ31 Mg alloy in the SBF is proposed.

A Ni- and Cu-free Zr-based bulk metallic glass with excellent resistance to stress corrosion cracking in simulated body fluids

Abstract In order to evaluate stress corrosion cracking (SCC) susceptibility of a Ni- and Cu-free Zr 56 Al 16 Co 28 bulk metallic glass (BMG) for biomedical application, the SCC behaviour of the BMG in various simulated body fluids (SBFs) including Hanks’, PBS(−) and 0.9% NaCl solutions open to air at 37 °C has been investigated using a slow strain rate technique (SSRT) at various initial tensile strain rates in the region of 5 × 10 −7 to 5 × 10 −4 s −1 . It was found that the Zr–Al–Co BMG exhibited excellent resistance to SCC in all of tested conditions. The amounts of cytotoxic cobalt ions released from the BMG disks of 5 mm in diameter were lower than those from the currently used biomaterial Co–Cr–Mo alloy. XPS analysis revealed that zirconium and aluminium ions were enriched in both air-formed and passive films. Moreover, these films were composed of double oxyhydroxide of zirconium, aluminium and cobalt. The formation of the stable and homogeneous double oxyhydroxide film enriched with zirconium and aluminium cations seems to be responsible for the high corrosion resistance and hence good SCC resistance of the Zr–Al–Co glassy alloy in SBFs. Thus, the Zr 56 Al 16 Co 28 BMG can be potentially promising material for biomedical applications.

Improved endothelialization of NiTi alloy by VEGF functionalized nanocoating

To improve surface endothelialization of NiTi alloy substrate, a nano-structured coating functionalized with vascular endothelial growth factor (VEGF) was fabricated via polydopamine (PDOP) as intermediate layer. The successful preparation of VEGF conjugated nanocoating was demonstrated by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), respectively. Inductively coupled plasma mass spectrometry (ICP-MS) test showed that the formed nanocoating significantly reduced the release of Ni ion from NiTi alloy in simulated body fluid. The biological behaviors of endothelial cells adhered to modified NiTi alloy substrates, including cell proliferation, cell spreading and production of nitric oxide and prostacyclin were investigated in vitro. The results suggest that surface functionalization of NiTi alloy substrate with VEGF is beneficial for cell growth. The approach presented here affords an alternative for surface modification of NiTi implants applied as heart and vascular implant devices.

Improved anticorrosion of magnesium alloy via layer-by-layer self-assembly technique combined with micro-arc oxidation

To enhance corrosion resistance of WE43 magnesium alloy, chitosan (CHI) and poly (styrene sulfonate) (PSS) polyelectrolyte multilayers were fabricated on micro-arc oxidation (MAO) treated magnesium alloy substrate via layer-by-layer (LBL) self-assembly technique. Surface morphology and chemical composition of the MAO/LBL composite coating were investigated by scanning electron microscopy (SEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. Potentiodynamic polarization test and hydrogen evolution measurement showed that the formed MAO/LBL coating significantly enhanced corrosion resistance of WE43 magnesium alloy in simulated body fluid (SBF). The approach presented here affords an effective alternative for surface modification of magnesium-based materials to meet the requirements of biomaterials applications.

Surface Modification and In Vitro Characterization of Cp-Ti and Ti-5Al-2Nb-1Ta Alloy in Simulated Body Fluid

Ti and its alloys are widely used in manufacturing orthopedic implants as prostheses for joint replacement because of their high corrosion resistance and excellent biocompatibility. However, they lack in bone-bonding ability and leads to higher rate of osteolysis and subsequent loosening of implants. In order to enhance the bone-bonding ability of these alloys, various surface-modification techniques are generally employed. The present investigation is mainly concerned with the surface modification of Cp-Ti and Ti-5Al-2Nb-1Ta alloy using a mixture of alkali and hydrogen peroxide followed by subsequent heat treatment to produce a porous gel layer with anatase structure, which enhances osseointegration. The morphological behavior was examined by x-ray diffractometer (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDX). The in vitro characterization of all the specimens was evaluated by immersing the specimens in simulated body fluid solution to assess the apatite formation over the metal surface. The apatite formation was confirmed by XRD, SEM-EDX, and Fourier transform infrared spectroscopy (FT-IR). Further, the electrochemical corrosion behaviors of both the untreated and treated specimens were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy. The results revealed that the surface-modified and heat-treated specimens exhibited higher corrosion resistance and excellent biocompatibility when compared to the chemical and untreated specimens.