Corrosion Resistance In Simulated Body Fluid Research Articles

Pulsed laser surface texturing enhancing corrosion resistance of rare-earth WE43 magnesium alloys in simulated body fluid environment

The addition of rare earth (RE) elements in Magnesium (Mg) alloys could optimize alloy microstructures and improve the mechanical property. The corrosion resistance however is a tough issue that limits its application as biomedical materials in human bodies. In this work, a green, fast and economical method of pulsed laser surface texturing (PLST) was employed to modify the RE WE43 Mg alloys and the corresponding corrosion resistance after the PLST treatment in simulated body fluid (SBF) was further examined. The microstructural results show that the surface exhibits petal-like microstructures and an oxide film composed of various oxides with remelting particles are also generated on laser-processed areas after PLST treatment. The electrochemical results reveal that the WE43 sample treated by PLST exhibits a superior corrosion resistance in SBF compared with the as-cast one. As for the PLST treated sample with 24 W, the corrosion potential (Ecorr) positively shifts from −1.788 V to −1.556 V after being immersed in SBF for 7 days, which is also nobler than that of the as-cast one, −1.915 V. While the corrosion current density (icorr) drops to the value of 8.3 μA/cm2, considerably lower than that of the as-cast sample, 1380 μA/cm2. The enhancement of corrosion resistance in the early stage is mainly due to the protective oxide film induced by PLST. Furthermore, long-term immersion in SBF further accelerates the formation of deposited hydroxyapatite (HA) products layer on petal-like microstructures, which would further contribute to its enhancement in corrosion resistance in the long-term service in human bodies.

Design of Ti-Mo-W Alloys and Its Correlation with Corrosion Resistance in Simulated Body Fluid (SBF)

Titanium and its based alloys are frequently selected for designing biomedical implants and it is thus necessary to study as detailed as possible their corrosion behavior in biological solutions, such as those in the human body environment. In this paper, with the use of molecular orbital calculation, we designed and developed alloys in the Ti-19Mo-xW system (x = 7, 8, 9, and 10 wt%) and investigated the influence of different contents of tungsten on the behavior of Ti-19Mo-xW alloy samples following corrosion in simulated body fluid (SBF). The values of Bo¯ (bond order) and Md¯ (the metal-orbital energy level) were calculated for each alloy and correlations were established between Bo¯ and the content of tungsten. It was found that with the increase in tungsten content, the value of Bo¯ increases. Regarding the values of the corrosion resistance in SBF that resulted from the investigated alloys, the Ti19Mo7W alloy is distinguished by the lowest value of the corrosion current density and the lowest corrosion rate.

A sol-gel based bioactive glass coating on laser textured 316L stainless steel substrate for enhanced biocompatability and anti-corrosion properties

In this study, we have synthesized a new family of bioactive glass (BAG) comprising of SiO2, Na2O, CaO, K2O, P2O5 and MgO via sol-gel route. The composition of these oxides has been selected in such a way that the BAG has a coefficient of thermal expansion close to the 316L stainless steel (SS). In vitro test by soaking the BAG in simulated body fluid (SBF) showed good bioactivity due to ion exchange between alkali ions from the BAG and the ions present in the SBF. The 316L SS substrates were textured using laser before application of BAG using sol-gel dip coating. Pull off test showed that the adhesion strength in case of textured and non-textured surfaces were 4.2 MPa and 2.46 MPa, respectively. This implies that texturing of the surface is helpful in increasing the adhesion strength of the coating. The bioactive glass-coated textured surface of 316L SS substrate showed better corrosion resistance in SBF than the bare substrate for which the respective corrosion current densities were 35 nA/cm2 and 353 nA/cm2, thereby indicating that the single layer sol-gel dip coating of bioactive glass improved the corrosion resistance of the 316L SS implants. The analysis of scanning electron microscopy (SEM) images of the coating after immersion in SBF shows the formation and growth of the apatite layer that will further inhibit the corrosion of the substrate. These results demonstrate the potential of the synthesized BAG as a coating material for 316L SS implants.

Development and assessment of a multifunctional chitosan-based coating applied on AZ31 magnesium alloy: Corrosion resistance and antibacterial performance against Klebsiella Pneumoniae

This work presents a simple method to functionalise the surface of AZ31 magnesium alloy by applying a duplex MgF 2 /chitosan coating, which improves its corrosion resistance and provides it with some antibacterial performance. First, the effect of three chitosan solutions with different concentrations on the growth of the bacteria Klebsiella pneumoniae in nutritive medium (TSB) was evaluated by absorbance kinetics experiments, where the chitosan solution at 2% (m/V) was selected for the coating preparation. Before coating application, the AZ31 substrate was pretreated with hydrofluoric acid for 48 hours in order to form a MgF 2 conversion layer. Subsequently, the coating was applied to the pretreated substrate through the dry-casting method. Samples of the alloy in each surface condition (bare, pretreated, and pretreated + coated with chitosan) were exposed to simulated body fluid (SBF) for 21 days at 37 °C, with the solution renewed every 24 hours and the wastes stored. The surfaces were characterised by SEM-EDS, and XPS after the immersion tests, whereas the stored solutions were employed to measure the change in the Mg-ions concentration. Electrochemical impedance spectroscopy and potentiodynamic polarisation were performed in each surface condition to compare their corrosion resistance in SBF. The antibacterial activity of the functionalised surfaces was evaluated by the plate counting method and compared with bare samples. All results were correlated and demonstrate that the modified surface of AZ31 achieved a higher corrosion resistance when it was exposed to SBF, as well as a reduction of the bacterial growth during in vitro tests.

Cu-Zr-Ti-Al metallic glass: Thermodynamic prediction, synthesis, and biocorrosion studies

In this study, glass forming composition (GFC) in Cu-Zr-Ti-Al system was predicted using thermodynamic guidelines involved model. The GFC was predicted by optimizing the enthalpy of chemical mixing and mismatch entropy in a statistically designed configurational entropy range. As designed composition Cu46Zr40Ti8.5Al5.5, close to eutectic point, was synthesized into metallic glass by melt spun technique. The amorphous nature of metallic glass was verified using XRD, DSC and TEM. The material was subjected to corrosion studies in simulated body fluids (SBF) at 37 °C using electrochemical polarization technique. The material has exhibited better corrosion resistance in comparison to conventional biomaterials. Enhanced corrosion resistance is attributed to amorphous nature of the material and stable passive film predominately containing ZrO2, Al2O3 and AlOOH. Further, it was observed that the substitution of Cu with Al and Zr in Cu-Zr-Ti metallic glass enhances the corrosion resistance in SBF.

Cu-Zr-Ti-Al Metallic Glass: Thermodynamic Prediction, Synthesis, and Biocorrosion Studies

Abstract In this study, glass forming composition (GFC) in the Cu-Zr-Ti-Al quaternary system was predicted using a thermodynamic guidelines involved model approach. Where, the GFC was predicted by optimizing the enthalpy of chemical mixing and the mismatch entropy in a statistically designed configurational entropy range. As designed composition Cu46Zr40Ti8.5Al5.5 (close to eutectic point) was synthesized into metallic glass by the melt spun technique. Amorphous nature of the metallic glass was verified using XRD, DSC and TEM. The material was subjected to corrosion studies under the simulated body fluids (SBF) at test at 37°C using electrochemical polarization technique to evaluate the biocompatibility. The material has exhibited better corrosion resistance in comparison to the existing conventional biomaterials . Enhanced corrosion resistance is attributed to amorphous nature of material and stable passive film predominately containing ZrO2, Al2O3 and AlOOH . Further it was observed that the substitution of Cu with Al and Zr in Cu-Zr-Ti metallic glass enhances the corrosion resistance in SBF.

Fabrication of superhydrophobic composite coating of hydroxyapatite/stearic acid on magnesium alloy and its corrosion resistance, antibacterial adhesion

The bacterial infection of bone implants is a vital factor leading to implant failure. Superhydrophobic surface with low adhesion can effectively enhance corrosion resistance and antibacterial adhesion properties of magnesium alloy. Herein, the superhydrophobic composite coating of hydroxyapatite (HA)/stearic acid was successfully prepared on magnesium alloy (AZ31B) using hydrothermal method and followed modification of stearic acid. The wettability, corrosion resistance and antibacterial adhesion capacity of the composite coating were studied. The composite coatings confer excellent superhydrophobicity with a contact angle about 152.52° and a sliding angle about 2°, and showed good long-term superhydrophobic stability in air. Meanwhile, during immersion in simulated body fluid (SBF), the superhydrophobic composite coating was converted to hydrophilicity in a short time and exposed the micro-/nano-scale structure surface of HA, which could induce the fast deposition of the mineralized apatite layer. The characteristics endowed the composite coating with the short-term antibacterial adhesion property and long-term corrosion resistance in SBF, which will afford a surface modification strategy for the application of magnesium alloy implants in orthopedics and dentistry.

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.

Morphological studies on the development of chemical conversion coating on surface of Mg–4Zn alloy and its corrosion and bio mineralisation behaviour in simulated body fluid

Nucleation and growth of chemical conversion coating on Mg–4Zn alloy prepared by immersion in saturated NaHCO3 at ambient temperature and its corrosion behaviour in simulated body fluid (SBF) is investigated in this paper. Compact dense coating obtained up on 24 h of immersion at ambient temperature is found to provide complete coverage of the surface and a high initial corrosion resistance in SBF. With sustained exposure to SBF, the coating dissolves and slowly cracks to expose the substrate to the corrosion medium. The 24 h coated sample shows high levels of bio mineralisation, with flower shaped crystals of phosphates of Ca and Mg on the surface. The combined effects of slow first hydrogen evolution rate and precipitation of phosphates, and similarities to the carbonate coating developed in vivo makes the conversion coating discussed in this paper a suitable choice for Mg alloys for temporary bio implant applications.

Correlation between Antimicrobial Activity and Bioactivity of Na-Mica and Na-Mica/Fluorapatite Glass and Glass-Ceramics and Their Corrosion Protection of Titanium in Simulated Body Fluid

The improvement in bioactivity of titanium (Ti) surface was achieved via coating it with Na-mica and Na-mica/fluorapatite glass and glass-ceramic using the low-cost electrophoretic deposition technique. Two compositions from pure Na-mica (M) and 80 Na-mica/20 fluorapatite glasses (MF) were prepared in the system SiO2-Al2O3-MgO-MgF2-Na2O-B2O3 using melting–quenching technique. Characterization of the as-prepared glasses and their counterpart glass-ceramics was studied using differential thermal analysis (DTA), x-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform-IR (FTIR) spectroscopy techniques. The bioactivity behavior was proved by studying the XRD, FTIR and SEM after immersing both glass and glass-ceramic samples in simulated body fluid (SBF). Both M and MF glasses and glass-ceramics showed high microhardness measurements and good antibacterial behavior. In vitro biodegradation was studied by using electrochemical corrosion behavior of the prepared glass- and glass-ceramic-coated Ti in SBF. The prepared coated Ti showed good corrosion resistance in SBF at 37 °C using potentiodynamic polarization technique, and the impedance data fitting explained the structure of the coating and the adsorption of SBF ions on the Ti surface. The MFGC provides the best corrosion-resistant coating, especially after sintering it.

Electrophoretic Deposition of Hydroxyapatite–Chitosan–Titania on Stainless Steel 316 L

In this research, hydroxyapatite (HA)–chitosan–titania nanocomposite coatings were formed on 316 L stainless steel using electrophoretic deposition (EPD) from alcoholic (methanol and ethanol) suspensions containing 0.5 g/L chitosan and 2 and 5 g/L HA and 2 and 5 g/L Titania. The effect of different parameters on the deposition rate, morphology, and corrosion resistance of the coatings in simulated body fluid (SBF) at 37 °C has been studied. The coatings’ properties were investigated using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Based on the results of this work, it was found that the deposition rate in ethanolic suspensions is lower than methanolic ones. Moreover, the coating surface was smoother when the ethanol was used as a solvent in suspensions in comparison to the ones where methanol was the solvent. The coating deposited from a suspension containing 0.5 g/L chitosan, 2 g/L HA, and 5 g/L titania with ethanol as solvent had the highest corrosion resistance in SBF at 37 °C.

Effect of surface treatment on the bioactivity and electrochemical behavior of magnesium alloys in simulated body fluid

The effect of surface treatment using NaOH or H2O2 on the bioactivity and corrosion behavior of AZX310, AZ91D, AM50, and AZ31 Mg alloys in simulated body fluid (SBF) has been studied with the aid of surface morphological assessment, in vitro characterization, and electrochemical measurements. The influence of immersion time on the behavior of the treated alloys in SBF was also investigated. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed successful surface modification upon treatment of alloy surface with NaOH and H2O2. XRD and SEM analyses also revealed that surface modification enhances formation and growth of hydroxyapatite (HA). Formation of HA layer on the alloy surface was further confirmed by Fourier transform infrared spectroscopy analysis. In vitro immersion test reveals that pH of SBF solution containing treated alloys is lower than that containing untreated alloy. However, pH increases with immersion time. Results from weight loss and electrochemical measurements indicate that treated alloys possess higher corrosion resistance in SBF than the untreated ones. H2O2 treated alloys demonstrated greater corrosion resistance in SBF than NaOH treated alloys.

Corrosion and bioactivity performance of graphene oxide coating on Ti[sbnd]Nb shape memory alloys in simulated body fluid

In the present work, the microstructure, corrosion, and bioactivity of graphene oxide (GO) coating on the laser-modified and -unmodified surfaces of TiNb shape memory alloys (SMAs) were investigated. The surface morphology and chemical composition was examined using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The surface modification was carried out via a femtosecond laser with the aim to increase the surface roughness, and thus increase the adhesion property. FE-SEM analysis of the laser-treated Ti-30at.% Nb revealed the increase in surface roughness and oxygen/nitrogen containing groups on the Ti-30at.% Nb surface after being surface modified via a femtosecond laser. Furthermore, the thickness of GO was increased from 35μm to 45μm after the surface was modified. Potentiodynamic polarisation and electrochemical impedance spectroscopy studies revealed that both the GO and laser/GO-coated samples exhibited higher corrosion resistance than that of the uncoated TiNb SMA sample. However, the laser/GO-coated sample presented the highest corrosion resistance in SBF at 37°C. In addition, during soaking in the simulated body fluid (SBF), both the GO and laser/GO coating improved the formation of apatite layer. Based on the bioactivity results, the GO coating exhibited a remarkable antibacterial activity against gram-negative bacteria compared with the uncoated. In conclusion, the present results indicate that Ti-30at.% Nb SMAs may be promising alternatives to NiTi for certain biomedical applications.

The effect of plasma nitriding temperature on the electrochemical and semiconducting properties of thin passive films formed on 316 L stainless steel implant material in SBF solution

In this study, 316L stainless steel samples were nitrided plasma at temperatures of 350, 400 and 450°C for 2h under a gas mixture of 50% N2–50% H2. The effect of plasma nitriding temperature on the corrosion performance and semiconductor properties of the passive film on the 316L stainless steel was evaluated in simulated body fluid (SBF) using electrochemical test and Mott–Schottky analysis. In literature study, the effect of plasma nitriding temperature on corrosion behavior of 316L stainless steel was evaluated in solutions of NaCl, H2SO4 and acidic for biomedical applications. However, corrosion studies are more suitable to test in simulated body solution. Also, there are no enough studies on the effects of plasma nitriding temperature on semiconductor properties of the passive film obtained on film 316L stainless steels in SBF solution. So, in this study the effects of plasma nitriding temperature on the electrochemical and semiconducting properties of thin passive films formed on 316L stainless steel implant material in SBF solution at 37°C were investigated. The effects of microstructure and phase structure on corrosion properties of samples were determined. The results showed that the phase composition and microstructure of the treated samples were affected from the nitriding temperatures. It was obtained that s-phase formed at the lower temperature than 400°C. According to electrochemical test results, the plasma nitriding process at 350°C was the most suitable process condition for improving the corrosion resistance in SBF. All oxide films showed p-type (acceptor) semiconductor behavior at low potentials and n-type (donor) behavior at high potentials.

Fatigue Behaviors of a Ni-free ZrCuFeAlAg Bulk Metallic Glass in Simulated Body Fluid

Fatigue behaviors of a biocompatible Ni-free Zr60.14Cu22.31Fe4.85Al9.7Ag3 Zr-based bulk metallic glass (BMG) have been studied under three-point-bending test in a simulated body fluid (SBF) at 37 °C and compared with those in air at room temperature (RT). The BMG shows a high fatigue limit of approximately 366 MPa in SBF, which was slightly lower than that in air (400 MPa). The fatigue cracks tended to initiate from the defects such as cast-pores, inclusions and corners of the samples and propagate in a similar path in SBF and in air. Three distinct regions, i.e. a crack-initiation region, a stable crack-growth region and an unstable fast-fracture region were clearly observed on the fatigue-fractured surface. Although pitting occurred at the defects where crack initiated, it does not affect significantly the fatigue life of the BMG, because the lifetime in the present BMG is mainly determined by crack propagation. The high corrosion-fatigue limit of the studied BMG results from its excellent corrosion resistance in SBF and intrinsically good toughness.

Microstructure, mechanical properties, biocorrosion behavior, and cytotoxicity of as-extruded Mg–Nd–Zn–Zr alloy with different extrusion ratios

Recently, commercial magnesium (Mg) alloys containing Al (such as AZ31 and AZ91) or Y (such as WE43) have been studied extensively for biomedical applications. However, these Mg alloys were developed as structural materials, not as biomaterials. In this study, a patented Mg–Nd–Zn–Zr (denoted as JDBM) alloy was investigated as a biomedical material. The microstructure, mechanical properties, biocorrosion behavior, and cytotoxicity of the alloy extruded at 320 °C with extrusion ratios of 8 and 25 were studied. The results show that the lower extrusion ratio results in finer grains and higher strength, but lower elongation, while the higher extrusion ratio results in coarser grains and lower strength, but higher elongation. The biocorrosion behavior of the alloy was investigated by hydrogen evolution and mass loss tests in simulated body fluid (SBF). The results show that the alloy extruded with lower extrusion ratio exhibits better corrosion resistance. The corrosion mode of the alloy is uniform corrosion, which is favorable for biomedical applications. Aging treatment on the as-extruded alloy improves the strength and decreases the elongation at room temperature, and has a small positive influence on the corrosion resistance in SBF. The cytotoxicity test indicates that the as-extruded JDBM alloy meets the requirement of cell toxicity.

Texture effect on corrosion behavior of AZ31 Mg alloy in simulated physiological environment

The texture effect of AZ31 Mg alloy on its corrosion resistance in simulated body fluid (SBF) at 37°C was examined by hydrogen evolution method, polarization curve and electrochemical impedance spectrum. It was found that at the early immersion time, the sample with c-axis of most grains normal to the exposed surface exhibited much higher corrosion resistance than the sample consisting mainly of (101¯0) and (112¯0) oriented grains. But after about 46h of immersion, the corrosion rate of both samples was largely reduced, less than 0.011ml/cm2/h due to the deposition of a film on surfaces. The profound texture effect on the corrosion resistance in SBF opened a new window to control the corrosion property of Mg alloys for biomedical applications.

Corrosion behavior of TiO2 films on Mg–Zn alloy in simulated body fluid

Magnesium alloys have been widely investigated in the field of biomaterials due to their moderate mechanical properties close to human bone and gradual degradation in human physiological environment without second surgeries. But results from clinical studies showed that magnesium implants suffered from too rapid degradation in human physiological environment. To reduce the degradation rate of magnesium alloys, surface modification is essential and effective besides element alloying. In this study, TiO2 films were deposited on Mg–Zn alloy by direct current reactive magnetron sputtering. The morphology and structure of the films were characterized by atomic force microscopy (AFM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The corrosion resistance in simulated body fluid (SBF) at 37°C was evaluated by potentiodynamic polarization and hydrogen evolution tests. The corrosion behavior of the samples was investigated by SEM with energy dispersive spectroscopy (EDS) after immersion for different periods. The results showed that the compact films were composed of particles with the size of about 100nm and could effectively improve the corrosion resistance in SBF. After immersion for 10 days, the corrosion rates of the substrates and samples with TiO2 films were 4.13mm/y and 1.95mm/y, respectively. During the immersion, the TiO2 films could induce the growth of hydroxyapatite (HAp) to improve the bioactivity of the samples.

Microstructure and Mechanical Properties and Corrosion Behavior of Ti-Mo-Sn Alloys

The phase constitution, mechanical properties, and corrosion behavior of TiMoSn alloys were investigated by means of XRD, tensile test, electrochemical measurement and XPS techniques. The XRD analysis results showed that at room temperature TiMoSn alloys are mainly composed of β phase, with minor content of α" phase, in as-cast and solid solution treated conditions. The tensile test results indicate that the elastic moduli of the Ti-Mo-Sn alloys are in the range of 52~74GPa. The electrochemical measurement results indicate that TiMoSn alloys have excellent corrosion resistance in simulated body fluid. The XPS analysis results reveal that the passive films of TiMoSn alloys after polarization consist of TiO2, SnO2 and Mo2O5.

Effect of calcium-ion implantation on the corrosion resistance and bioactivity of the Ti6Al4V alloy

The corrosion resistance and bioactivity of Ti6Al4V alloy after calcium-ion implantation were examined. Polished samples were implanted with a dose of 10 17 Na +/cm 2 at a beam energy of 25 keV. The chemical composition of the surface layer formed during the implantation was determined by XPS and SIMS. The bioactivity of the samples was evaluated by soaking them in a simulated body fluid (SBF) at 37 °C for 168 and 720 h. The corrosion resistance in SBF at 37 °C was determined by electrochemical methods after exposure in SBF for various times. The surfaces of the samples before and after examinations were observed by optical microscopy, SEM-EDS and AFM. The results of the corrosion examinations indicated that under stationary conditions and after short-term exposures, the calcium-ion implanted titanium alloy had an increased corrosion resistance, but during the anodic polarization, calcium-implanted samples underwent pitting corrosion. The microscopic observations show that the precipitations of calcium phosphates are present on the surface, but they do not form a continuous layer.