Surface Of AZ31B Magnesium Alloy Research Articles

Effect of Acrylic Resin on the Protection Performance of Epoxy Coating for Magnesium Alloy

The low toughness of epoxy resin can influence its shielding performance against a corrosive medium and strength of adhesion to metal surfaces. Extensive efforts have been made to modify epoxy resin. In this research, acrylic resin was synthesized by the solution method, and 1 wt.%, 2.5 wt.%, and 5 wt.% were added to epoxy resin (E44 brand) to prepare coatings on the surface of AZ31B magnesium alloy. The effects of acrylic resin on the mechanical and protective properties of epoxy coatings were investigated via experiments measuring impact resistance, flexibility, and adhesion as well as the electrochemical impedance technique. Compared with the pure epoxy coating, the adhesion between the coating and the substrate increases by 1.37 MPa after the addition of 2.5 wt.% acrylic resin. Meanwhile, the pencil hardness has a slight change from 5B to 6B, and the flexibility significantly improves. Therefore, the epoxy coating exhibits enhanced anticorrosive properties after the addition of 2.5 wt.% acrylic resin.

Passivation of surface of AZ31B magnesium alloy in solutions based on salts of rare-earth metals

Новые технологии, Химическая промышленность, Химическая технология, Научные журналы, Защита от коррозии, Технология металлов, Свойства материалов, Технические журналы, Наука и технологии, Справочная литература, Научные разработки

Effect of Zinc Phosphating Pretreatment on NiP Electroless coating on AZ31B Magnesium Alloy Surface

Effect of Zinc Phosphating Pretreatment on NiP Electroless coating on AZ31B Magnesium Alloy Surface

Passivation of the surface of AZ31B magnesium alloy in solutions based on salts of rare-earth metals

Passivation of the surface of AZ31B magnesium alloy in solutions based on salts of rare-earth metals

Construction of Chi(Zn/BMP2)/HA composite coating on AZ31B magnesium alloy surface to improve the corrosion resistance and biocompatibility

Abstract As biodegradable orthopedic implant materials, magnesium alloys have been attracted enough attentions recently. However, too fast degradation in vivo, limited biocompatibilities, and insufficient antibacterial properties are three main challenges at present. In order to solve these problems, a multifunctional composite coating of Chi(Zn/BMP2)/HA was constructed on AZ31B magnesium alloy surface, successively by the alkali heating treatment, self-assembly of 16-phosphonyl-hexadecanoic acid, in situ immobilization of Chi(Zn/BMP2) (chitosan, zinc ions, and bone morphogenetic protein 2), and the deposition of HA (hydroxyapatite). The results of ATR-FTIR (attenuated total reflection Fourier transform infrared spectrum) spectra and elemental compositions confirmed that 16-phosphonyl-hexadecanoic acid, Chi(Zn/BMP2), and HA were successfully immobilized on the surface. Compared with Mg, Mg-OH, Mg-16, and Mg-Chi(Zn/BMP2), Mg-Chi(Zn/BMP2)/HA with the concave–convex structure surface significantly enhanced the hydrophilicity and corrosion resistance. On the other hand, Mg-Chi(Zn/BMP2)/HA coating also showed excellent biocompatibilities, which not only significantly promoted the osteoblast adhesion and proliferation, but also upregulated ALP and OCN expression of osteoblasts. Furthermore, due to the synergistic antibacterial effect of zinc ions and chitosan, Mg-Chi(Zn/BMP2)/HA showed a good antibacterial property against Escherichia coli (E. coli). Therefore, it can be said that the method used in this work has a good application prospect in improving the corrosion resistance, biocompatibility of magnesium alloys, and inhibiting infections against E. coli.

Effect of the laser texturing width on hot-pressing joining of AZ31B and CFRTP

Laser texturing was performed on the surface of AZ31B magnesium alloy to increase the bonding strength. Textured AZ31B and carbon fiber reinforced thermoplastics (CFRTP) were then joined by the hot-pressing joining process. The effect of various groove widths of laser textured grid on the AZ31B/CFRTP joint was investigated. The research results showed that the wettability of the molten CFRTP on laser textured AZ31B was increased by about nine times, and the contact angle was reduced from 104.0° to 48.8° with a groove width of 0.3 mm. The macroscopic morphology and interface of joints had no defects, when the groove widths were 0.2 mm and 0.3 mm. The tensile-shear test was carried out, and the maximum tensile-shear force of the joint was 2698.8 N in the case of 0.3-mm groove width, which was 2.1 times as much as that of the untreated joint. The maximum tensile-shear force was 65.43% of the CFRTP itself. A diffusion layer of 9 μm– 24 μm thick formed at the AZ31B/CFRTP joint. MgCO3 was identified at the joining interface. The mechanical interlocking and chemical bonding formed at the interface effectively improved the strength of the joint.

Hydrothermal synthesis of hydroxyapatite coating on the surface of medical magnesium alloy and its corrosion resistance

The early corrosion control of biomedical magnesium alloy is an important measure to determine its good performance during implantation into human body. The deposition of calcium phosphate biological coating is the most effective solution at present. In this paper, hydroxyapatite (HAP) coating was hydrothermal synthesized on the surface of AZ31B magnesium alloy, and the influence mechanism of hydrothermal synthesis temperature, time and solution concentration was investigated. The synthesis conditions and deposition mechanism of hydroxyapatite coating without DCPA (CaHPO4) were proposed. The surface morphology of the coating was observed by field emission electron scanning microscope (FESEM). The types and contents of microelements in the material were analyzed by energy disperse spectroscopy (EDS). Fourier transform infrared spectroscopy (FTIR) was used to analyze the functional group information of the coating surface. The corrosion resistance of different experimental groups was studied by electrochemical test. The results showed that when the calcium phosphate solution concentration was 0.1 ​mol/L and the calcium/phosphorus ratio was 1.67, the coating had better morphology structure and corrosion resistance, and the calcium/phosphorus ratio of HAP crystals reached 1.58, the epit of the prepared AZ31B-HAP coating by bare metal increased from −1.51 ​V to −1.18 ​V, the impedance value reached 1.0 ​× ​105 ​Ω▪cm2, and the early corrosion of magnesium alloy substrate was effectively delayed.

High‐speed wire electrical discharge machining to create superhydrophobic surfaces for magnesium alloys with high corrosion and wear resistance

AbstractHerein, a superhydrophobic surface of AZ31B magnesium alloy prepared by high‐speed wire electrical discharge machining and modification with stearic acid is reported. The surface morphology and wettability of the superhydrophobic surface were investigated by scanning electron microscopy and optical contact angle measurement, respectively. A uniform micro‐/nanopetal‐like structure was shown within the superhydrophobic surface, resulting in a contact angle of 151 ± 0.5° and a sliding angle of 4 ± 0.5°. Notably, the superhydrophobic surface had better corrosion resistance than the bare magnesium alloy, and its corrosion current density was reduced by nearly one order of magnitude. Under both dry and wet friction conditions, the friction coefficient of the superhydrophobic surface was lower than that of the bare magnesium alloy surface, with a much lower wear loss. In addition, the friction coefficient of the superhydrophobic sample was lower than that of the bare magnesium alloy sample under both the dry and wet friction conditions. Thus, the superhydrophobic sample experienced reduced wear and had a low wear rate.

Low adhesion superhydrophobic AZ31B magnesium alloy surface with corrosion resistant and anti-bioadhesion properties

Low adhesion superhydrophobic surface plays a critical role in improving corrosion resistant and anti-bioadhesion properties of the substrates. In this study, a low adhesion superhydrophobic surface with robust hierarchical rough structure has been successfully fabricated on the AZ31B magnesium alloy via a facile and green two-step in situ immersion method and post-modification with stearic acid (SA), which are carried out at room temperature without oxidants, high temperature, or pressure. The two-step in situ immersion method involves a pre-immersion in a low-concentration MnSO4 solution and a post-immersion in a high-concentration MnSO4 solution, which enhances the interfacial bonding between the coating and substrate and helps to increase the stability of superhydrophobic surface. The obtained superhydrophobic coating exhibits strong adhesive force to the surface of AZ31B with arbitrary shapes, ultralow adhesion to water, and robustness. The robust low adhesion superhydrophobic AZ31B (LAS-Mg) strongly enhances corrosion resistance and displays anti-bioadhesion property against proteins, bacteria, and cells adhesion. The results have suggested that the LAS-Mg can be used in medical devices.

Effect of CoSO4 on the characteristics of micro-arc oxidation coatings

ABSTRACTOxidation coatings were prepared on the surface of AZ31B magnesium alloy by micro-arc oxidation in the electrolytes with CoSO4 addition varying from 0 to 0.8 g/L. The effects of different concentrations of CoSO4 on the properties and microstructure of the coating were analysed by Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD) and Electrochemical Workstation. The results revealed that the addition of different concentrations of CoSO4 caused the voltage variation, which resulted in the changes of microstructure, phase composition and element distribution of coatings. Furthermore, it led to the improvement of coating properties. It was found that the oxidation voltage increased firstly and then decreased. Because of CoSO4 addition, the morphology of the coating was changed. XRD patterns and XPS confirmed that Co3O4, MgO and Mg2SiO4 were generated. The addition of CoSO4 could effectively improve the hardness, corrosion resistance and thermal-shock resistance.

Fabrication of chitosan/heparinized graphene oxide multilayer coating to improve corrosion resistance and biocompatibility of magnesium alloys.

Due to its good biodegradability and mechanical properties, magnesium alloys are considered as the ideal candidate for the cardiovascular stents. However, the rapid degradation in human physiological environment and the poor biocompatibility seriously limit its application for biomaterials. In the present study, a chitosan/heparinized graphene oxide (Chi/HGO) multilayer coating was constructed on the AZ31B magnesium alloy surface using layer-by-layer (LBL) method to improve the corrosion resistance and biocompatibility. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectrum (RAMAN), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that a dense and compact Chi/HGO multilayer coating was fabricated on the magnesium alloy surface. The results of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), pH value changes and magnesium ion release suggested that the multilayer coating can significantly enhance the corrosion resistance of the magnesium alloy. Moreover, the Chi/HGO multilayer coating could not only significantly reduce the hemolysis rate and platelet adhesion, but also promote the adhesion and proliferation of endothelial cells. Therefore, the Chi/HGO multilayer coating can simultaneously improve the corrosion resistance and biocompatibility of the magnesium alloys.

Temporary Inhibition of the Corrosion of AZ31B Magnesium Alloy by Formation of Bacillus subtilis Biofilm in Artificial Seawater.

It is well known that microorganisms tend to form biofilms on metal surfaces to accelerate/decelerate corrosion and affect their service life. Bacillus subtilis was used to produce a dense biofilm on an AZ31B magnesium alloy surface. Corrosion behavior of the alloy with the B. subtilis biofilm was evaluated in artificial seawater. The results revealed that the biofilm hampered extracellular electron transfer significantly, which resulted in a decrease of icorr and increase of Rt clearly compared to the control group. Moreover, an ennoblement of Ecorr was detected under the condition of B. subtilis biofilm covering. Significant reduction of the corrosion was observed by using the cyclic polarization method. All of these prove that the existence of the B. subtilis biofilm effectively enhances the anti-corrosion performance of the AZ31B magnesium alloy. This result may enhance the usage of bio-interfaces for temporary corrosion control. In addition, a possible corrosion inhibition mechanism of B. subtilis on AZ31B magnesium alloy was proposed.

Corrosion behavior of porous ZrO2 ceramic coating on AZ31B magnesium alloy

Magnesium alloys have been recognized as promising implant materials because of their biodegradability. However, rapid degradation due to electrochemical corrosion compromises their cytocompatibility and mechanical integrity. In the present work, a porous ZrO2 ceramic coating was constructed on the surface of AZ31B magnesium alloy (ZrO2-AZ31B) to improve its corrosion resistance. The corrosion resistance of the coating was evaluated in simulated body fluid solution by electrochemical techniques. Higher open circuit potential, impedance and polarization resistance of ZrO2-AZ31B indicate it has a better corrosion resistance than that of AZ31B substrate in simulated body fluid solution. The results suggest that fabricating a ZrO2 ceramic coating on magnesium alloys is an effective method to decrease the degradation rate of magnesium alloys thereby better matching clinical requirements.

Friction-stir processing of a cold sprayed AA7075 coating layer on the AZ31B substrate: Structural homogeneity, microstructures and hardness

In this study, the cold gas dynamic spraying (CGDS) process was employed to modify the surface of AZ31B magnesium alloy with an aluminum-zinc alloy (AA7075). Friction-stir processing (FSP) was subsequently applied as a solid-state localized surface modification technique to improve the structure and integrity of the cold sprayed layer, by enhancing densification, homogeneity, and microstructural features of the as-deposited material. The structure of precipitates and grains were also refined due to the applied severe plastic deformation during FSP, which ultimately affects the indentation hardness resistance of the processed AZ31B-AA7075 bi-metallic structure. Microscopy indicated slight grain coarsening within the AZ31B substrate occurred simultaneously with refinement of the AA7075 coating, along with significant hardness improvements of ~80% and 30% respectively for each region in terms of Vickers hardness after FSP.

Laser Surface Melting and Strengthening Magnesium Alloy far from Equilibrium

In order to obtain extremely rapid solidification structure far from equilibrium, the surface of AZ31B magnesium alloy was melted by CO2 laser, while the samples were extremely rapidly cooled in liquid nitrogen. The microstructure, the performance and the strengthening mechanism of the laser melted layer were investigated. The results show that grains of the melted layer are highly refined and the grain size is nearly uniform. The melted layer contains α-Mg and β-Mg17Al12, but β-Mg17Al12 which distributes along the grain boundary is few. Because of strengthening mechanisms of fine grains, super solid solution and dislocation, microhardness HV of the melted layer is up to 1400 MPa. Wear loss of the melted sample cooled in liquid nitrogen is about 50% less than that of the untreated sample and the melted sample cooled in air, and wear resistance of the melted layer is improved obviously. Impacting fracture morphology indicates that there is a trace of plastic deformation, thus, improving plasticity and ductility.

Corrosion resistance of AZ31B magnesium alloy with a conversion coating produced from a choline chloride—Urea based deep eutectic solvent

A novel ionothermal strategy for developing a chemical conversion film on magnesium alloys is proposed based on the interaction of a deep eutectic solvent (DES) with the substrate. Upon heating the choline chloride/urea mixture-based DES can react with the AZ31B magnesium alloy surface to form a promising anti-corrosion conversion film. Interestingly, the chemical conversion film is mainly composed by MgH2 and MgCO3 phases. The as-grown conversion film exhibits superhydrophobicity after surface modification in a stearic acid/ethanol solution. Electrochemical tests and visual investigations indicate the corrosion resistance of the magnesium alloy can be improved by the conversion film.

Corrosion characterization of micro-arc oxidization composite electrophoretic coating on AZ31B magnesium alloy

A two layer composite coating system was applied on the surface of AZ31B magnesium alloy by Micro-arc Oxidation (MAO) plus electrophoretic coat (E-coat) technique. The Mg sample coated with MAO plus E-coat (MAOE) was compared with bare Mg and Mg sample coated by MAO only. The surface microstructure and cross section of bare and coated Mg before and after corrosion were examined by Scanning Electron Microscopy (SEM). The corrosion performance of bare and coated Mg was evaluated using electrochemical measurement and hydrogen evolution test. The results indicated that the corrosion resistance of AZ31B Mg alloy was significantly improved by MAOE composite coating. The corrosion mechanism of bare and coated Mg is discussed.

Research on the Preparation of Magnesium Alloy Micro-Arc Oxidation Black Ceramic Membrane

Black ceramic membranes are made on the surface of AZ31B magnesium alloy to further study the micro-arc oxidation coloring ceramic membranes with more colors.In the system of sodium silicate - copper sulfate, black ceramic membrane with good compactness and uniform color can be made while the concentration of sodium silicate is 20g/L and the concentration of copper sulfate is 1.0g/L. Experimental results show that the chroma of the membrane varies from light color system to deep color system with the increasing content of copper aluminum compounds.

Effect of Na 2 SiO 3 solution concentration of micro-arc oxidation process on lap-shear strength of adhesive-bonded magnesium alloys

Micro-arc oxidation films are fabricated on the surface of AZ31B magnesium alloy in the Na2SiO3 electrolyte. The mechanical performance of magnesium alloy bonding with the adhesive is examined by single lap-shear test, and the morphology and composition of the oxidation film are characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The data indicate that the increase of Na2SiO3 solution concentration results in the decrease of bonding strength of magnesium alloy joints, while the porosity has no directly relation with the variation of the lap-shear strength. The results also show that Na2SiO3 participates into the film formation and the fabricated film is mainly composed of MgO and Mg2SiO4. In particular, with the increase of Na2SiO3 solution concentration, the content of MgO decreased while that of Mg2SiO4 increased. Moreover, MgO could initiate the formation of the hydroxyl group, which potentially enhances surface wettability and hydrogen bonding with the adhesive. This rationale is strongly supported by the results of Fourier Transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measuring.

Femtosecond laser-induced iridescent effect on AZ31B magnesium alloy surface

Both micro-ripples and nano-ripples were firstly reported at AZ31B magnesium alloy surface irradiated by femtosecond laser in atmospheric environment. Iridescent effect was also demonstrated over a large area of the irradiated surface induced by scanning laser beam. Results revealed that the colour effect was mainly attributed to the nano-ripples with broad distribution of periods acting as diffraction gratings, and intensity of the structural colour was greatly influenced by morphology evolution of the micro-ripples with laser processing. It was suggested that near-field interference between surface plasmons polaritons and incident laser light determined the formation of the nano-ripples, and initial surface roughness combing with such interference lead to the formation of the micro-ripples. Potential applications of such effect on Mg alloys and how to apply the technique to other materials with different properties was further proposed.