Alloy In Simulated Body Fluid Research Articles

Effect of Three Different Electrolyte Additives on Corrosion Resistance of Micro-arc Oxidation Coating of NiTi Alloy in Simulated Body Fluid

Effect of Three Different Electrolyte Additives on Corrosion Resistance of Micro-arc Oxidation Coating of NiTi Alloy in Simulated Body Fluid

Biodegradable magnesium alloy coated with TiO2/MgO two-layer composite via magnetic sputtering for orthopedic applications: A study on the surface characterization, corrosion, and biocompatibility

In this study, a coating of thin TiO2 layer and a TiO2/MgO double layer were created on the surface of AZ91D alloy by magnetic sputtering method in order to improve the corrosion and biocompatibility properties of this alloy. The microstructural studies by field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) showed that coatings were formed continuously and homogeneously on the alloy surface. In the double-layer coating, MgTiO3 and Mg2TiO4 compounds were formed at the coating/substrate interface in addition to TiO2 and MgO phases as the main phases in the coating structure. The results of corrosion test showed that in general, coating improves the corrosion of AZ91D alloy in simulated-body fluid (SBF). The double-layer coating showed the best corrosion resistance at a corrosion current of 5.743 × 10−7 μA/cm2 and a corrosion potential of −1.513 V due to its cathodic protection of the substrate and blockage of the path of the corrosive solution towards the substrate. In vitro tests showed that considering the good match between the used materials as the coating and body, no toxic material exits which results in improvement in biocompatibility, adhesion, and bone-cell multiplication.

Compositional dependence of the apatite formation ability of Ti-Zr alloys designed for hard tissue reconstruction.

Ti-Zr alloys are expected to be novel biomaterials with low stress shielding owing to their lower Young's moduli than pure Ti. The drawback of metallic biomaterials is that their bone-bonding abilities are relatively low. NaOH and heat treatments have been performed to provide Ti-50Zr with apatite-forming ability in the body environment, which is essential for bone bonding. However, the systematic compositional dependence of apatite formation has not been revealed. In the present study, NaOH treatment of Ti-Zr alloys with various compositions and bone-bonding abilities was assessed in vitro by apatite formation in simulated body fluid (SBF). The corrosion current density in NaOH aqueous solution and the amount of Na incorporated into the surface tended to decrease with increasing Zr content. The apatite-forming ability of the treated alloy significantly decreased when the Zr content was ≥60 atom%. This phenomenon is attributed to the (1) low OH content on the surface, (2) low Na incorporation into the treated alloy surface, which enhances apatite formation, and (3) low ability of P adsorption to the Ti-Zr alloy in SBF following Ca adsorption to trigger apatite nucleation. Although the adhesion of the titanate/zirconate layer formed on the surfaces to the substrates increased as Zr content increased, the adhesion between the apatite and the substrate was still low.

Corrosion Degradation Behavior of Forged Mg-Zn-Zr/-Y Alloy in Simulated Body Fluid

The corrosion degradation rate of pure magnesium and forged Mg-Zn-Zr/-Y magnesium alloy was compared by static immersion corrosion weight loss experiment and electrochemical corrosion experiment at constant temperature (37±0.5°C) and room temperature (25±1°C) SBF to simulate the corrosion degradation rate in body fluids. The results show that the corrosion resistance of magnesium alloy can be improved by adding Zn, Zr, Y compared with pure magnesium. The results of static immersion corrosion test and electrochemical corrosion test of forged Mg-Zn-Zr-Y show that the corrosion resistance of magnesium alloy can be improved by adding Zn, Zr, Y element. The average corrosion rate of the forged Mg-Zn-Zr-Y alloy was 0.62mm/a by weight loss method after 240 h immersion corrosion in SBF at 37 ± 0.5 °C, and the corrosion resistance of forged Mg-Zn-Zr-Y alloy was better than Mg-Zn-Zr alloy.

Microstructure, Mechanical Properties, and in Vitro Corrosion Behavior of Biodegradable Zn-1Fe-xMg Alloy.

Zinc (Zn), one of the promising candidates for biodegradable implant materials, has excellent biocompatibility and biodegradability. In this study, as-cast Zn1FexMg (x ≤ 1.5 wt %) alloys were prepared to systematically explore the effects of magnesium (Mg) alloying on their microstructures, mechanical properties, and biodegradability. The microstructure of Zn1FexMg alloy consisted of Zn matrix, Zn + Mg2Zn11 eutectic structure, and FeZn13 phase. The addition of Mg not only promoted grain refinement of the alloy, but also improved its mechanical properties. The results of immersion tests showed that the addition of Mg accelerated microcell corrosion between different phases, and the modeling of the corrosion mechanism of alloys in simulated body fluid (SBF) solution was discussed to describe the interaction between different phases in the corrosion process. Zn1Fe1Mg possessed superior comprehensive mechanical properties and appropriate corrosion rate, and the values for hardness, tensile strength, yield strength, elongation, and corrosion rate were 105 HB, 157 MPa, 146 MPa, 2.3%, and 0.027 mm/a, respectively, thus revealing that Zn1Fe1Mg is a preferred candidate for biodegradable implant material.

Correlation between the crystallized structure of Mg67Zn28Ca5 amorphous alloy and the corrosion behavior in simulated body fluid

The corrosion behavior of Mg-Zn-Ca amorphous alloys in simulated body fluid is of academic and engineering interests since they are potential biomaterials. The influence of the crystallized structure of the Mg67Zn28Ca5 amorphous alloy on the corrosion behavior in simulated body fluid (SBF) is investigated. The different crystallized structures were obtained by heating the amorphous sample to temperatures of 100 °C~300 °C. The results reveal that the amorphous Mg67Zn28Ca5 alloy shows better corrosion resistance in SBF than partially crystallized samples, and homogeneous chemical corrosion occurs on the surface of the amorphous alloy. In contrast, inhomogeneous galvanic corrosion occurs on the surfaces of the partially crystallized Mg67Zn28Ca5 sample; and the corroded surface becomes more rugged with increasing the crystallized temperature. The corrosion rate (Vcorr) of the Mg67Zn28Ca5 amorphous alloy in SBF shows a nearly linear relation with the crystallized volume fraction (CVF), i.e., Vcorr= −8.38+96.23CVF, indicating that its corrosion behavior is readily tuned by crystallization.

Effect of Twin-Induced Texture Evolution on Corrosion Resistance of Extruded ZK60 Magnesium Alloy in Simulated Body Fluid

Different pre-compression deformations are carried out along the extrusion direction of ZK60 magnesium alloy to change the initial texture of the material. The corrosion resistance of ZK60 magnesium alloy associated with twin-induced texture evolution was investigated by immersion and electrochemical experiments in simulated body fluid (SBF). The results showed that a small amount of twins decreased corrosion resistance, while high density twins improved the corrosion resistance of the material.

Microstructure and properties of monolayer, bilayer and multilayer Ta2O5-based coatings on biomedical Ti-6Al-4V alloy by magnetron sputtering

In recent years, tantalum pentoxide (Ta2O5) ceramic coating has attracted considerable attention in the modification of implants due to its excellent biocompatibility, high corrosion resistance, and good wear resistance. However, the poor adhesion to the substrate degrades its performance and may become a significant obstacle to its clinical application. In the paper, Ta2O5 monolayer, Ta2O5/Ti bilayer, and Ta2O5/Ta2O5-Ti/Ti multilayer coatings were prepared on the Ti-6Al-4V alloy by magnetron sputtering. The microstructure, chemical composition, residual thermal stress, adhesion strength, mechanical properties, tribological behaviors, and corrosion resistance of the coatings were investigated and compared. The results showed that these deposited coatings were composed of an amorphous nano-Ta2O5 phase, and their surfaces were smooth, dense, and homogeneous without any cracks. Ta2O5/Ta2O5-Ti/Ti coatings exhibited lower thermal residual stress than that of the Ta2O5 and Ta2O5/Ti coatings, which could be attributed to the decrease of the coefficient of thermal expansion (CTE) mismatch between the Ta2O5 film and Ti-6Al-4V substrate due to the introduction of the Ta2O5-Ti/Ti double-interlayer. Moreover, Ta2O5/Ta2O5-Ti/Ti coating was significantly superior to Ta2O5 and Ta2O5/Ti coatings in the adhesion strength, mechanical properties, and wear resistance. These Ta2O5-based coatings can provide excellent corrosion protection for Ti-6Al-4V alloy in simulated body fluids (SBF). The Ta2O5 monolayer coating samples showed the best corrosion resistance, mainly due to its thick out-layer Ta2O5 film. These experimental results provide a feasible way to improve the performances of Ta2O5 coating on Ti-6Al-4V alloy.

Improving stress corrosion cracking behavior of AZ31 alloy with conformal thin titania and zirconia coatings for biomedical applications

Magnesium and its alloys have been widely studied as materials for temporary implant devices. However, corrosion-assisted cracking phenomena such as stress corrosion cracking (SCC) continue to prevent their mainstream use. For the first time, we explore the SCC susceptibility of Atomic Layer Deposition (ALD) coated AZ31 alloys in Simulated Body Fluid (SBF). Conformal 100 nm coatings of titania and zirconia were deposited on standard dogbone specimens and subjected to slow strain rate tests at 3.5 10-6 s-1 and a temperature of 37 °C. Remarkably, the SCC susceptibility index IUTS was reduced by 6% and 40% and the Iε was reduced by more than 70% and 76% with a titania and zirconia coating, respectively. Potentiodynamic polarization, hydrogen evolution and fracture behavior of the samples revealed the drastic corrosion reduction to be the main reason for the susceptibility reduction. We discuss the observed SCC behavior of our samples in light of the coatings’ electrochemical activities, wettabilities, surface integrities and mechanical properties. This straightforward conformal surface treatment can be useful as a workaround for one of the major bottlenecks of biomedical Mg based implants and hence provides a possible pathway for making them more commonplace in the field.

Effect of D-fructose on the in-vitro corrosion behavior of AZ31 magnesium alloy in simulated body fluid

The effect of adding d-fructose to simulated body fluid (SBF) on the corrosion behavior of AZ31 magnesium (Mg) alloy at 37 °C and at a pH of 7.4 was studied by potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), potentiostatic polarization and hydrogen (H2) collecting techniques, Raman spectroscopy technique, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy analysis (XPS) and Fourier transformed infrared (FTIR). The results demonstrated that the addition of fructose enhanced the deposition of phosphates forming thick and compact corrosion products, which inhibited the transmission of aggressive ions into the Mg substrate. As a result, both the anodic dissolution of Mg and negative difference effect (NDE) were suppressed. Thus, the corrosion resistance of AZ31 Mg alloy in SBF was significantly improved.

Role of Vanadium Additions on the Corrosion Mitigation of Ti-6Al-xV Alloy in Simulated Body Fluid

The manufacturing of different Ti-6Al-xV (x = 2, 4, 6, and 8 wt.%) alloys using a mechanical alloying technique was reported. The corrosion behaviors of these newly fabricated alloys after 1, 24, and 48 h exposure to a simulated body fluid (SBF) were assessed using cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and chronoamperometric measurements. Surface morphology and elemental analyses after corrosion for 48 h in SBF were reported using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) examinations. An X-ray diffraction investigation characterized the phase analyses. All results indicated that the increase of V content significantly decreases both uniform and pitting corrosion. This effect also increases with prolonging the immersion time to 48 h before measurement.

Corrosion and Biocompatibility Behavior of the Micro-Arc Oxidized AZ31B Alloy in Simulated Body Fluid

Corrosion and Biocompatibility Behavior of the Micro-Arc Oxidized AZ31B Alloy in Simulated Body Fluid

Effect of precipitation hardening on stress corrosion cracking susceptibility index of AZ31B magnesium alloy in simulated body fluid

Research work elaborates ways of improving stress corrosion cracking susceptibility index of AZ31B magnesium alloy through solutionizing and precipitation strengthening. Specimens solutionized at 420 °C for 20 h and precipitation strengthened at 200 °C for 6 h, 12 h, and 18 h were tested by using slow strain rate tensile testing in air and simulated electrolyte i.e., Hank’s balanced salt solution at a strain rate of 10−4 per sec. For percentage elongation, maximum stress corrosion cracking (SCC) susceptibility index was obtained for 6 h aged sample. For ultimate tensile stress, maximum SCC susceptibility index was obtained for 12 h aged sample.

Effects of Sr addition on microstructure, mechanical and corrosion properties of biodegradable Mg–Zn–Ca alloy

Abstract Selection of non-toxic elements existed in human body or certified for tissue regeneration is considered for multifunctional biodegradable metals. The effect of Sr addition on microstructure, mechanical properties, and degradation behavior of biodegradable Mg–2Zn-0.3Ca alloy was studied as an example to gain insight into the Mg–Zn–Ca alloy series. The average grain size of alloys became smaller and more homogeneous distinctly by increasing Sr content. The second phases on the grain boundaries and the interdendritic interstices were also refined with small amount of Sr addition. More concentration of Sr element was detected evidentially at the interface between grains and the second phases. Mg–2Zn-0.3Ca-0.3Sr alloy shows the optimal flexural and compressive strength of (441 ± 18) MPa and (317 ± 13) MPa, respectively. The electrochemical measurement in simulated body fluid showed that addition of Sr would slightly deteriorate the corrosion resistance of Mg–Zn–Ca–Sr alloys. The in-vitro immersion tests were conducted and analyzed in detail by three different immersion stages and got a distinctive corrosion performance compared with the electrochemical measurements. Homogenization annealing was conducted for Mg–2Zn-0.3Ca-0.3Sr alloy, which can reduce dendrite segregation and significantly improve the corrosion resistance of alloy. The degradation process of alloys in simulated body fluid was summarized in detail for Mg–Zn–Ca–Sr alloys. This work not only provides the relationship between microstructure and properties of biodegradable Mg alloys, but also a comprehensive discussion of degradation behavior of Mg–Zn–Ca alloys for orthopedic application.

Comparing physiologically relevant corrosion performances of Mg AZ31 alloy protected by ALD and sputter coated TiO2

The utilization of Mg alloys for biomedical applications is so far underexplored due to the accelerated corrosion hampering patient recovery post implantation. Here, we explore the effectiveness of corrosion reduction of an AZ31 alloy in Simulated Body Fluid when coated with a 40 nm sputtered TiO2 layer and compare it to a similar coating made by Atomic Layer Deposition (ALD). Potentiodynamic polarization and hydrogen evolution experiments were performed on coated samples having different surface roughness and 3D topologies. Interestingly, ALD layers reduce corrosion current density by 94% on Ra = 118.6 ± 5.1 nm and 93% on Ra = 4794.3 ± 49.4 nm, whereas sputtered only by 84% on Ra = 118.6 ± 5.1 nm and 60% on Ra = 4794.3 ± 49.4 nm. Particularly on 3D aspects, the ALD coatings are superior, where a scaffold of 85% porosity with 1 mm pore sizes released 68% lower hydrogen compared to the sputtered counterparts. We relate these observations to the higher surface integrity, adhesion strength and lower line-of-sight restrictions of ALD compared to sputter deposition. The results can be interesting for researchers and practitioners aiming to make Mg alloys more commonplace as temporary metallic implant materials.

Insight into role and mechanism of Li on the key aspects of biodegradable ZnLi alloys: Microstructure evolution, mechanical properties, corrosion behavior and cytotoxicity.

ZnLi based alloys have been proved as desirable candidates for biodegradable materials accounting for its high mechanical performance and great biocompatibility. However, effects of Li on microstructure and comprehensive properties of Zn alloys are seldom investigated and need to be addressed. Herein, Zn-(0.1-1.4wt%)Li alloys are fabricated and systematically analyzed. Lath-like Zn precipitates are observed in the primary β-LiZn4 (β) phase of Zn-(0.5-1.4wt%)Li alloys, leading to the formation of dense β/Zn lamellar structure with an inter-spacing of 0.8μm. Mechanical tests show that the strengths of the ZnLi alloys have at least tripled due to the formation of dense β/Zn lamellar structure. Early degradation behaviors of the ZnLi alloys in simulated body fluid (SBF) reveal a competitive releasing of Li+ and Zn2+. As the priority of Li+ releasing becomes more obvious with increasing Li content in the alloys, aqueous insoluble Li-rich corrosion products containing LiOH and Li2CO3 form a passivation film on Zn-(0.5-1.4wt%)Li alloys. Consequently, corrosion rate decreases significantly from 45.76μm/y of pure Zn to 14.26μm/y of Zn-1.4Li alloy. Importantly, observations of white light interferometer microscope and transmission electron microscope demonstrate that β phase degrades prior to Zn in the alloys, suggesting that biomedical implants made of ZnLi alloys are likely to degrade completely in human body. Cytotoxicity tests of the alloys exhibit no cytotoxicity in 10% extracts. The most tolerated Zn2+/Li+ concentrations of the alloy extracts to L-929 cells are calculated, which provides guidance for future design of Zn alloys containing Li.

Electrochemical corrosion behavior of a magnesium calcium alloy in simulated body fluids with different glucose concentrations

This paper investigates the effect of glucose concentration on the electrochemical corrosion behavior of a magnesium calcium alloy in Hanks’ simulated body fluid (SBF) using potentiodynamic polarization and electrochemical impedance spectrum (EIS) methods. The results indicate that the corrosion potential of magnesium calcium alloy decreased slightly from −1.34V to −1.49V with increasing the glucose concentration from 0.7g/L to 1.6g/L. Comparatively, the corrosion current density decreased from 2.038mA/cm2 to 0.031mA/cm2, indicating that the corrosion rate was inhibited effectively by a high glucose concentration. Crevice corrosion was found to be a dominant corrosion mode under all investigated glucose concentrations. In addition, wet peening treatment was proved to be a promising method to improve the corrosion resistance of magnesium calcium alloy. The corrosion rates were decreased by over 60% using wet peening treatment. The research provides a fundamental understanding of the corrosion behavior and associated corrosion mechanism of magnesium calcium alloy within different body fluid environments.

The Effect of Ni Content on the Corrosion Resistance of Some Fe–Cr–Ni Alloys in Simulated Body Fluids in the Presence of H2O2 and Albumin

The stainless steel alloys are greatly utilized for human orthopaedic and implants. The electrochemical behaviour of the stainless steel of Fe–17Cr–xNi alloys (x = 8, 10, 14) has been studied in simulated body fluid containing H2O2 and albumin at 37 °C. The electrochemical behaviour of the Fe–17Cr–8Ni, Fe–17Cr–10Ni and Fe–17Cr–14Ni has been investigated using the potentiodynamic polarization and electrochemical impedance spectroscopy, EIS. The surface morphology of the three alloys was examined before and after immersion in the simulated body fluid containing H2O2 and albumin using scanning electron microscope. The elemental composition of the oxide layer formed on the surface of the alloys after immersion in the electrolyte was obtained using energy dispersive X-ray analysis, EDX, technique. The metals released into the electrolyte has been determined using atomic absorption spectrophotometry. The EIS and potentiodynamic polarization results demonstrate that the Fe–Cr–14Ni alloy attains highest polarization resistance and the smallest rate of corrosion than Fe–17Cr–8Ni and Fe–17Cr–10Ni alloys. Fe–17Cr–14Ni is slightly influenced by immersion in simulated body fluid containing H2O2 and albumin which is confirmed by SEM images and metal release via formation of protective passive film. The surface analysis has shown the participation of the different alloying elements in the passive film.

The effect of Equal Channel Angular Pressing on the stress corrosion cracking susceptibility of AZ31 alloy in simulated body fluid

Despite the great potential of Mg and its alloys as material for biodegradable implants, their low resistance to the simultaneous action of corrosion and mechanical stresses in the human body have hampered their use. Stress Corrosion Cracking has been reported as one of the most critical failure modes to overcome to allow such materials to be clinically applied. Thus, in this paper we investigate the effect of Equal Channel Angular Pressing (ECAP) on the Stress Corrosion Cracking (SCC) susceptibility of the AZ31 Mg alloy. To do so, AZ31 alloy has been subjected to 1, 2 and 4 passes of ECAP, and the samples so obtained have then been tested by means Slow Strain Rate Tests (SSRTs) in Simulated Body Fluid (SBF) at 37 °C. Samples subjected to one pass of ECAP are shown to be less susceptible to SCC compared to the material in the as-received condition, while further ECAP processing (2 and 4 passes) are found to worsen the SCC susceptibility. To understand the different SCC susceptibilities shown by the differently ECAPed samples, microstructural analyses, potentiodynamic polarization curves, hydrogen evolution experiments and Scanning Electron Microscopy (SEM) analyses of the fracture surfaces were carried out. The improved corrosion resistance of the samples subjected to 1 pass of ECAP compared to the samples in the as received condition (due to a finer grain size) and to the samples subjected to 2 and 4 passes (due to a more favourable texture evolution) represents the reason of their reduced SCC susceptibility.

A High-Strength and Biodegradable Zn–Mg Alloy with Refined Ternary Eutectic Structure Processed by ECAP

In this study, the microstructure, mechanical properties and corrosion behaviors of a Zn–1.6Mg (wt%) alloy during multi-pass rotary die equal channel angle pressing (RD-ECAP) processing at 150 °C were systematically investigated. The results indicated that a Zn + Mg2Zn11 + MgZn2 ternary eutectic structure was formed in as-cast Zn–Mg alloy. After ECAP, the primary Zn matrix turned to fine dynamic recrystallization (DRX) grains, and the network-shaped eutectic structure was crushed into fine particles and blended with DRX grains. Owing to the refined microstructure, dispersed eutectic structure and dynamically precipitated precipitates, the 8p-ECAP alloy possessed the optimal mechanical properties with ultimate tensile strength of 474 MPa and elongation of 7%. Moreover, the electrochemical results showed that the ECAP alloys exhibited similar corrosion rates with that of as-cast alloys in simulated body fluid, which suggests that a high-strength Zn–Mg alloy was successfully developed without sacrifice of the corrosion resistance.