Bio-corrosion Resistance Research Articles

Inhibition effect on microbiologically influenced corrosion of Ti-6Al-4V-5Cu alloy against marine bacterium Pseudomonas aeruginosa

With rapid development of marine infrastructures, materials with better biocorrosion resistance and antibiofouling performance will be highly demanded. Ti6Al4V alloy is susceptible to the above. The inhibition to the microbiologically influenced corrosion of Ti6Al4V-5Cu alloy against Pseudomonas aeruginosa was investigated using antibacterial test, electrochemical techniques, surface analysis, and weight loss test conducted for 2.5 months. At a sputtering depth of 0 nm, the passive film of Ti6Al4V-5Cu alloy was mainly composed of ideal oxide TiO2. With increasing sputtering thickness to 6 nm, Ti2O3 and TiO were detected with a relative fraction of 14.6% and 14.8%, respectively, in the oxide layer of Ti6Al4V-5Cu alloy. In contrast, the outermost layer of Ti6Al4V alloy was predominantly composed of TiO2 but Ti2O3 (22.8%), Al2O3 and V2O5 were also detected. With increasing sputtering depth to 6 nm, fitting revealed the presence of Ti2O3 and TiO with relative fractions of 25.3% and 35.8%, respectively. Yet, a spot of TiO (8%) was also observed at 12 nm in the oxide layer of Ti6Al4V alloy. Although the addition of Cu into Ti6Al4V alloy generated the self-healing property of passive film in the presence of P. aeruginosa, it also reduced resistance to corrosion in general condition.

Enhanced Bio-corrosion Resistance by Cu Alloying in a Micro-alloyed Pipeline Steel

On the composition base of commercial X65 grade pipeline steels, a Cu modified pipeline steel was designed to show improved resistance to microbially induced corrosion (MIC). The mechanical properties of the Cu-added steel and its corrosion behavior in a soil solution inoculated with sulfate-reducing bacteria (SRB) were investigated in this work. The results demonstrated that Cu-added steel exhibits a good combination of strength and toughness. Cu ions released from the Cu-added steel could effectively kill the SRB attaching on the steel surface, thus evidently decreased the pit depth and diameter of Cu-added steel. Furthermore, during the long-term immersion, the Cu-rich film formed by the enrichment of Cu in the corrosion product layer on the steel surface could also contribute to the improvement of the bio-corrosion resistance of Cu-added steel.

Development of HAp/GO/Ag coating on 316 LVM implant for medical applications

In this study, antibacterial activity, biocompatibility, and corrosion resistance of 316 LVM implants were improved using the development of HAp/GO/Ag nanocomposite coatings by the dip-coating method. The XRD and FTIR results confirmed the synthesis of HAp/GO/Ag nanocomposites. HAp/Ag nanoparticles (68 nm) bound to epoxy, hydroxyl, and carboxyl functional groups on GO sheets (size of GO sheets varies from 255 to 1480 nm) by electrostatic interaction. FESEM images showed that HAp/GO/Ag coatings had higher density and fewer micro-cracks than pure HAp coatings. In addition, HAp/GO/Ag coatings showed optimized nano-hardness (4.5 GPa) and elasticity modulus (123 GPa). The results of potentiodynamic polarization demonstrated that HAp/GO/Ag coating has the lowest corrosion current density (0.31 μA/cm2), maximum protection efficiency (90.0%), and lowest release of Fe, Cr, and Ni ions (31, 24, and 15 ppb). In addition, EIS results showed that HAp/GO/Ag coatings could prevent electrolyte access to the substrate and provide high bio-corrosion resistance. A bone-like layer is formed on nanocomposite coatings after 28 days in SBF, proving that Ag and GO's addition does not interfere with the mineralization process. After 28 days of immersion in SBF, the lowest release of Fe, Cr, and Ni ions is related to nanocomposite coatings. Also, the release of Ag+ ions from the coatings is between 0.13 and 1.41, providing antibacterial activity without cytotoxicity. HAp/GO, HAp/Ag, and HAp/GO/Ag nanocomposites kill 47%, 92%, and 98% of E. coli bacteria, respectively. HAp/GO, HAp/Ag, and HAp/GO/Ag nanocomposites kill 47%, 92%, and 98% of E. coli bacteria, respectively. The cell culture results showed that human MG-63 osteoblast-like cells in contact with HAp/GO/Ag coating had the highest biocompatibility (98% of cells survived). Therefore, the development of HAp/GO/Ag nanocomposite coating on 316 LVM implant shows improved properties of nano hardness, corrosion resistance, antibacterial activity, and biocompatibility properties, which is a new turning point for nanocomposite coatings for medical applications.

Plastic anisotropy and compressive deformation behavior of Zinc prepared by sintering using fine particles

In recent years, Zn can potentially be applied as biomaterials owing to its excellent biocompatibility and biocorrosion resistance. However, Zn has poor strength and large plastic anisotropy due to its hexagonal close-packed (HCP) structure. In this study, to increase the strength and plastic isotropy, fine-grained Zn polycrystal was produced by spark plasma sintering from Zn fine particles prepared by arc plasma method. Yield strength and the plastic anisotropy of the sintered Zn were evaluated by compression tests and Vickers indentation. The yield strength of the sintered Zn was significantly higher than the as-cast Zn. Moreover, the plastic anisotropy of the sintered Zn was small because of its fine grain and random texture.

Low cost porous Ti-6Al-4 V structures by additive manufacturing for orthopaedic applications

Ti-based alloys have exceptional features such as super-elasticity, shape memory effect, superior bio-corrosion resistance, satisfactory Young's modulus, and brilliant bio-compatibility intended towards bio-implant usage. However, solid Ti alloys have higher mechanical strength and modulus of elasticity, hence porous structures have been used instead of solid Ti alloy to get similar results as compared to human bones. Extensive research has been done to produce porous Ti alloy scaffolds with a lower modulus of elasticity and higher compressive strength as a substitute for human bones by varying porosity and input parameters. Three different types of scaffolds (Tesseract, Star, and Octet) with 65 % porosity were modelled in Rhino 6 software and constructed through route of additive manufacturing (AM), notably Selective Laser Melting or SLM of Ti-6Al-4 V powders. Then microstructures, mechanical characteristics and porosities of the Ti alloy scaffolds were investigated. The compressive test of porous Ti-6Al-4 V scaffolds were conducted by INSTRON machine with load capacity ± 25 kN and from results it is found that the modulus of elasticity of Tesseract, Star and Octet scaffolds are 10.78 GPa, 9.29 GPa and 8.61 GPa respectively which are similar to human bones (3–30 GPa). This work primarily focuses on advantages and performances of porous titanium scaffolds to serve the needs of orthopaedic applications. Due to its higher heating rate and lower hold time, AM technologies, notably SLM, can also build scaffolds withnanoscale grain. The desired function is typically not realised by this strategy, which leads to inadequate compaction. The scaffolds made by SLM have a reasonably good pore structural accuracy but moderate mechanical strength. Star type scaffolds have a greater manufacturing ability than other scaffolds, with a smaller porosity percentage error.

Multifaceted Ag-alloyed α-Ta5Si3 nanostructured coating for high-performing bioimplants

With the growth of the elderly population worldwide especially in developed countries, bioimplants with a multifunctional surface that embraces self-sterilizing trait, biocompatibility with mammalian cells, favorable bioactivities and high wear/corrosion resistance are in acute need. To meet such demand, the Ag-containing nanostructured α-Ta 5 Si 3 coating was fabricated onto Ti6Al4V alloy via double cathode glow discharge method. The effect of Ag addition on the mechanical properties of α-Ta 5 Si 3 was analyzed using first-principles calculations. The as-deposited α-(Ta 0.85 Ag 0.15 ) 5 Si 3 coatings consist of equiaxed nanocrystallites and greatly enhance the surface hardness of Ti6Al4V alloy. Moreover, the electrochemical characteristic, apatite-inducing ability, biocompatibility and antimicrobial trait of the α-(Ta 0.85 Ag 0.15 ) 5 Si 3 coatings were systematically studied for potential orthopedic application. The new coatings were found to remarkably reduce the corrosion damage of Ti6Al4V alloy in Ringer's solution. The coatings also promoted the formation of bone-like apatite layers and have a beneficial effect on MC3T3-E1 cells functions, including adhesion, spreading and proliferation. Ag alloying markedly increased the antibacterial capacity of the α-Ta 5 Si 3 coating against both Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ) strains, and the released Ag ions were found to enhance antibacterial performance. Therefore, a unique combination of diverse functional traits makes Ag-alloyed α-Ta 5 Si 3 coating an attractive choice in the design of next-generation biomedical implants for aging population. • The (Ta 0.85 Ag 0.15 ) 5 Si 3 coating improves biocorrosion resistance of Ti-6Al-4 V alloy. • Ag addition enables the antibacterial activities of the coating against both E. coli and S. aureus . • The (Ta 0.85 Ag 0.15 ) 5 Si 3 coating enhances the cytocompatibility and in vitro bioactivity of Ti-6Al-4V alloy. • Ag ion release plays a major role in the antibacterial performance of the coating.

Design and properties of novel Ti–Zr–Hf–Nb–Ta high-entropy alloys for biomedical applications

The novel high-entropy alloys (HEAs) with compositions of (Ti1/3Zr1/3Hf1/3)15(Nb1/2Ta1/2)x (x = 3, 5) for biomedical applications have been designed and synthesized, using the cluster formula approach. The present HEAs have a single body-centered-cubic (BCC) solid-solution structure and possess prominent mechanical properties of high compressive yield strength (834–890 MPa) and microhardness (287–293 Hv), large plasticity (>45%) under compression, as well as low Young's moduli (56–68 GPa). Also, these HEAs exhibit good bio-corrosion resistance, as revealed by a low corrosion rate at the order of 10−4 mm/year and the low passive current densities of 10−2 – 10−1 A/m2, which are attributed to the formation of passive films consisting of Ti-, Zr-, Hf-, Nb-, and Ta- oxides. The high cell viability and proliferation of bone-forming MC3T3-E1 cells on the HEAs are comparable to those on the Ti–6Al–4V alloy, indicating their good biocompatibility. The present work demonstrates the great potential of these novel Ti–Zr–Hf–Nb–Ta HEAs for biomedical applications.

The study of morphological evolution, biocorrosion resistance, and bioactivity of pulse electrochemically deposited Hydroxyapatite/ZnO composite on NiTi superelastic alloy

In this work, the effect of zinc oxide nanoparticles on hydroxyapatite deposited on NiTi superelastic alloy was studied. Various concentrations of nanoparticles (200, 400, and 800 mg/L) along with cetrimonium bromide (100 mg/L) as a dispersant agent were added to the coating electrolyte. Morphological observations showed that zinc oxide encouraged hydroxyapatite plate-like crystals to grow in longitudinal and transverse directions, turning into a bone-like structure with greater pores. XRD and FTIR indicated the favorable impact of zinc oxide on the synthesis of pure hydroxyapatite as the most stable calcium phosphate phase. Next, the corrosion evaluations revealed that zinc oxide successfully reduced the corrosion current density of composite coatings down to 1.35 nA/cm2, where pure calcium phosphate coating exhibited 19.05 nA/cm2. Topographic evaluations (AFM) proved a consistent rise in roughness parameters where the roughness average climbed from 208.3 nm for calcium phosphate coating up to 436.45 nm for the composite coating with the highest ZnO concentration. The adhesion strength of composite coatings was above 15 MPa (the critical requirement for orthopedic applications), despite calcium phosphate coating. The wettability results also differed dramatically where calcium phosphate coating exhibited 31.17°, but it dropped to 12.62° for the composite coating formed in the solution containing 400 mg/L ZnO nanoparticles. Ultimately, bioactivity analysis in simulated body fluid revealed that ZnO nanoparticles not only promoted growth but also restricted the size distribution of cauliflower-like apatite grains.

Bio-corrosion behavior, antibacterial property and interaction with osteoblast of laser in-situ fabricated Ti–Si–Cu coatings on Ti–6Al–4V alloy

Ti–Si–xCu coatings (TS-xC, x = 5, 10 and 15 wt.%) with advanced bio-corrosion resistance, excellent antibacterial property and biocompatibility were laser cladded on Ti–6Al–4V (TAV) substrate which is widely used as endosseous implants. The bio-corrosion resistance of the TAV substrate was improved due to the presence of Ti5Si3 and TiCu phases in the coatings. The addition of Cu in the precursor contributes to the improvement of the antibacterial property of TAV substrate. Meanwhile, induced normal cytoskeleton, well-developed focal adhesion contacts, significant higher cell attachment and proliferation rate were observed for the TS-xC coated samples due to the formation of micro-textured morphology and presence of new phases. The bio-corrosion resistance and antibacterial property depend on Cu content addition in the TS-xC precursor. The results provide a way to fabricate such multiple functional biocoating that would improve the bio-corrosion resistance, antibacterial performance and biocompatibility of TAV.

Formation and properties of biocompatible Ti-based bulk metallic glasses in the Ti–Cu–Zr–Fe–Sn–Si–Ag system

The Ni-free Ti-based bulk metallic glasses (BMGs) with high glass-forming ability (GFA) can be synthesized in the (Ti, Cu, Zr)92.5Fe2.5Sn2Si1Ag2 alloy system over a wide composition range by copper-mold casting. Especially, the Ti48Cu37Zr7.5Fe2.5Sn2Si1Ag2 glassy alloy can form the BMG rod with a diameter up to 6 mm and showed a high compressive strength of ~ 2.05 GPa, elastic modulus of ~ 100 GPa, and microhardness of ~ 571 Hv. The Ti-based BMGs presented good bio-corrosion resistance in a simulated physiological environment attributed to the formation of Ti-, Zr-, Si-, and Fe-enriched passive films. The biocompatibility of the Ti-based glassy alloys was systematically investigated by both indirect cytotoxicity test and direct cell-culture experiments. The Ti-based BMG extracts had no cytotoxic effects on the proliferation of the cells. The good cell adhesion, proliferation, differentiation, and mineralization of bone-forming MC3T3-E1 pre-osteoblasts on the BMGs were parallel to those on the Ti–6Al–4V alloy. These results manifested that the present Ti-based BMGs are promising candidates as biomaterials.

Compressive and biocorrosion properties of Ti-XAl-2Fe-3Cu alloys fabricated by powder metallurgy

Ti-XAl-2Fe-3Cu (wt%) (X = 2.7,4) alloys were fabricated by extrusion of compacts of TiH2/Al/Fe/Cu powder blends. The microstructure and compressive and biocorrosion properties of the as-extruded rods were studied and compared to those of commercial pure (CP) Ti fabricated by extrusion of a TiH2 powder compact under the same condition. The results show that the Ti-XAl-2Fe-3Cu alloy samples exhibit a significantly higher hardness and compressive yield strength than the CP Ti sample, and with increasing the Al content from 2.7 to 4 wt%, the compressive yield strength of the alloy increases from 1315 to 1422 MPa. The Ti-XAl-2Fe-3Cu alloy samples possess a better biocorrosion resistance than CP Ti, and the polarization resistance of the alloy increases with increasing Al content due to the reduced diffusion rate of corrosive ions through the surface oxide layers. Furthermore, with increasing the immersion time, the polarization resistance increases, and the double layer capacitance decreases. Overall the alloys show significantly better compressive strength and biocorrosion resistance than CP Ti, suggesting that they are more favorable than CP Ti for biomedical applications.

Effect of Mn addition on the microstructure, mechanical properties and corrosion resistance of a biodegradable Mg–Gd–Zn alloy

The effect of 0.5 and 1 wt% Mn additions on the microstructure, mechanical properties, and biocorrosion resistance of an extruded Mg–3Gd–1Zn (GZ31) alloy was investigated. Mn addition refined the grain structure so that the grain size decreased from 3.7 μm for the GZ31 alloy, to 2.3 μm for GZ31–1Mn alloy. Hardness measurements and shear punch tests (SPT) revealed that by adding 1 wt% Mn, the hardness, shear yield stress (SYS) and ultimate shear strength (USS) increased from 61 to 66 Hv, 102.0 to 128.5 MPa, and 142.8 to 152.4 MPa, respectively. The main mechanisms responsible for the improvement of mechanical properties were grain refinement and higher volume fraction of the second phase particles formed by Mn addition. Electrochemical impedance spectroscopy showed that the addition of 1 wt% Mn increased the overall corrosion resistance from about 515.4 Ω cm2 to 5883.6 Ω cm2. In addition, initiation of the inductive loop in the Nyquist diagrams of the Mn-containing alloys, in the lower frequencies in comparison to the base alloy, can be a sign of retarding the onset of pitting corrosion. The improved corrosion resistance of these alloys was due to the refined microstructure and formation of a more stable protective layer on the surface.

Exploration of WO3/BiVO4 composite based hot-dip zinc coating to combat biocorrosion

Herein, we report about the exploration of composite hot-dip zinc coating developed by integrating WO3/BiVO4 composite particles into the coating matrix with long-term stability and enhanced biocorrosion resistance. The composite zinc coating with tuned composition exhibits enhanced inhibition towards bacterial growth along with low survival percentage of bacteria on its surface. The improved antibacterial activity of the composite coating is ascribed to the presence of WO3/BiVO4 composite particles having narrow bandgap and reduced electron-hole recombination rate to generate reactive oxygen species on the coating surface. The composite coating retains high corrosion inhibition efficiency in aggressive marine environments and biocorrosion resistance in selected bacterial cultures. The stability and antibacterial activity of the composite coating are evidenced from the retention in surface characteristics even after 28 days of exposure in the bacterial media. The developed coating fulfils all the requirements for sustained prevention of biocorrosion and offers potential scope for practical use in marine environments.

In vitro investigation on microstructure, bio-corrosion properties and cytotoxicity of as-extruded Mg–5Sn–xIn alloys

The microstructure, bio-corrosion properties and cytotoxicity of as-extruded Mg–5Sn–xIn (x = 0, 1, 2, 3, 4, all in wt%) alloys were investigated in vitro for biomedical applications. The results show that the microstructure of all alloys exhibits a partially recrystallized structure, and the area fraction of dynamically recrystallized (DRXed) grains increases with In addition. Mg2Sn particles are mostly precipitated at DRXed grains. Weight loss and potentiodynamic polarization measurements show that the bio-corrosion resistance of as-extruded Mg–5Sn–xIn alloys is enhanced with increasing In content as a result of cathodic reaction being hindered by indium oxide deposition on the alloy surfaces. The Mg–5Sn–4In alloy exhibits the minimum corrosion rate of 0.36 mm/y after immersion in Hank’s solution for 15 days. The cytotoxicity tests reveal that the as-extruded Mg–5Sn–xIn alloys do not induce toxicity to murine fibroblast cells (NIH3T3) and Human Umbilical Vein Endothelial Cells (HUVECs). The HUVECs morphology is ameliorated in the alloys with In addition, which is greatly associated with decreasing corrosion rate. Thus, this study uses In as an effective alloying element to tune the corrosion property of Mg–Sn based alloys with low degradation and excellent cytocompatibility.

Corrosion Behavior and Osteogenic Activity of a Biodegradable Orthopedic Implant Mg–Si Alloy with a Gradient Structure

A gradient Mg-8 wt % Si alloy, which was composed of the agglomerated Mg2Si crystals coating (GMS8-1) and the eutectic Mg–Si alloy matrix (GMS8-2), was designed for biodegradable orthopedic implant materials. The bio-corrosion behavior was evaluated by the electrochemical measurements and the immersion tests. The results show that a significant improvement of bio-corrosion resistance was achieved by using the gradient Mg–Si alloy, as compared with the traditional Mg-8 wt % Si alloy (MS8), which should be attributed to the compact and insoluble Mg2Si phase distributed on the surface of the material. Especially, GMS8-1 exhibits the highest polarization resistance of 1610 Ω, the lowest corrosion current density of 1.7 × 10−6 A·cm−2, and the slowest corrosion rate of 0.10 mm/year. In addition, GMS8-1 and GMS8-2 show better osteogenic activity than MS8, with no cytotoxicity to MC3T3-E1 cells. This work provides a new way to design a gradient biodegradable Mg alloys with some certain biological functions.

Layer-by-Layer Self-Assembly Composite Coatings for Improved Corrosion and Wear Resistance of Mg Alloy for Biomedical Applications

Mg alloys are promising biomedical metal due to their natural degradability, good processability, and favorable mechanical properties. However, the poor corrosion resistance limits their further clinical applications. In this study, the combined strategies of surface chemical treatment and layer-by-layer self-assembly were used to prepare composite coatings on Mg alloys to improve the biocorrosion resistance. Specially, alkalized AZ91 Mg alloy generated chemical linkage with silane via Si–O–Mg covalent bond at the interface. Subsequently, Si–OH group from silane formed a crosslinked silane layer by Si–O–Si network. Further chemical assembly with graphene oxide (GO), lengthened the diffusion pathway of corrosive medium. The chemically assembled composite coatings could firmly bond to Mg alloy substrate, which persistently and effectively acted as compact barriers against corrosion propagation. Improved biocorrosion resistance of AZ91 Mg alloy with self-assembly composite coatings of silane/GO was subsequently confirmed by immersion tests. Besides, the Mg alloy exhibited good wear resistance due to outside layer of GO with a lubricant effect. Cell viability of higher than 75% had also been found for the alloy with self-assembly composite coatings, which showed good cytocompatibility.

Antimicrobial Zr-based bulk metallic glasses for surgical devices applications

Zr58.6Al15.4(Co1-xCux)26 (at. %; x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8) bulk metallic glasses (BMGs) were designed and produced by copper mold casting. As a result of the partial substitution, Zr58.6Al15.4Co18.2Cu7.8 (x = 0.3) BMG showed the largest glass glass formation ability with a critical glass forming diameter of 10 mm. And the Zr58.6Al15.4Co18.2Cu7.8 BMG also showed excellent room-temperature mechanical property, corrosion resistance and antibacterial property. The compressive strength (σf) was about 1.95 GPa and the plastic strain was about 2.0%. The corrosion current density was two order of magnitude lower than that of Ti6Al4V alloy. Moreover, antibacterial test results showed the surface of the BMG is able to eradicate bacteria at a 99.99% level. Therefore, for Zr60.5Ti3Al9Fe4.5Cu23 BMG, the properties combine with larger GFA, outstanding mechanical properties, biocorrosion resistance and antibacterial properties is considered a potential biomedical material for surgical devices applications.

Ti-Cu-Zr-Fe-Sn-Si-Ag-Pd Bulk Metallic Glasses with Potential for Biomedical Applications

Ti47Cu38−xZr7.5Fe2.5Sn2Si1Ag2Pdx (x = 1, 2, 3, and 4 atomic percent, at. pct) bulk metallic glasses (BMGs) with potential for biomedical applications were fabricated by copper-mold casting. The Ti-based BMGs exhibited high glass-forming ability (GFA) with critical diameters of 4 to 5 mm and a supercooled liquid region over 50 K, though the high contents of Pd slightly decreased the GFA. The additions of 2 and 3 at. pct Pd benefited the improvement of plasticity, and the resultant BMGs showed the relatively low Young’s modulus of about 100 GPa, high compressive strengths of 2174 to 2340 MPa, and compressive plastic strain of around 4 pct. The addition of Pd also decreased the passive current density and increased the pitting potential of the Ti-based BMGs in the Hank’s solution, leading to the enhanced bio-corrosion resistance of the BMGs. Furthermore, the cell adhesion, viability, and proliferation behaviors revealed that the present Ti-based BMGs possess as good biocompatibility as that of the Ti-6Al-4V alloy. These results demonstrated the potential of the Ti-Cu-Zr-Fe-Sn-Si-Ag-Pd BMGs as biomedical materials.

Antimicrobial TiO2 nanocomposite coatings for surfaces, dental and orthopaedic implants.

Engineering of self-disinfecting surfaces to constrain the spread of SARS-CoV-2 is a challenging task for the scientific community because the human coronavirus spreads through respiratory droplets. Titania (TiO2) nanocomposite antimicrobial coatings is one of the ideal remedies to disinfect pathogens (virus, bacteria, fungi) from common surfaces under light illumination. The photocatalytic disinfection efficiency of recent TiO2 nanocomposite antimicrobial coatings for surfaces, dental and orthopaedic implants are emphasized in this review. Mostly, inorganic metals (e.g. copper (Cu), silver (Ag), manganese (Mn), etc), non-metals (e.g. fluorine (F), calcium (Ca), phosphorus (P)) and two-dimensional materials (e.g. MXenes, MOF, graphdiyne) were incorporated with TiO2 to regulate the charge transfer mechanism, surface porosity, crystallinity, and the microbial disinfection efficiency. The antimicrobial activity of TiO2 coatings was evaluated against the most crucial pathogenic microbes such as Escherichia coli, methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Legionella pneumophila, Staphylococcus aureus, Streptococcus mutans, T2 bacteriophage, H1N1, HCoV-NL63, vesicular stomatitis virus, bovine coronavirus. Silane functionalizing agents and polymers were used to coat the titanium (Ti) metal implants to introduce superhydrophobic features to avoid microbial adhesion. TiO2 nanocomposite coatings in dental and orthopaedic metal implants disclosed exceptional bio-corrosion resistance, durability, biocompatibility, bone-formation capability, and long-term antimicrobial efficiency. Moreover, the commercial trend, techno-economics, challenges, and prospects of antimicrobial nanocomposite coatings are also discussed briefly.

Microstructure refinement, mechanical and biocorrosion properties of Mg–Zn–Ca–Mn alloy improved by a new severe plastic deformation process

In this study, the microstructural evolution, mechanical properties and biocorrosion performance of a Mg–Zn–Ca–Mn alloy were investigated under different conditions of heat treatment, extrusion, one pass and two passes of half equal channel angular pressing (HECAP) process. The results showed significant grain refinement of the homogenized alloy after two passes of HECAP process from 345 µm to 2 µm. Field emission scanning electron microscopy (FESEM) revealed the presence of finer Mg 6 Zn 3 Ca 2 phase as well as α-Mn phase after HECAP process. The results also showed that mechanical characteristics such as yield strength, ultimate tensile strength and elongation of the HECAPed samples improved by ∼208%, ∼144% and ∼100% compared to the homogenized one, respectively. Crystallographic texture analysis indicated that most of the grains at the surface were reoriented parallel to the (0001) basal plane after HECAP process. Electrochemical corrosion tests and immersion results indicated that the sample with two passes of HEACP had the highest biocorrosion resistance confirming that the basal planes had the lowest corrosion rate compared to the non-basal ones. The mechanical behavior and bio-corrosion evaluation demonstrated that the HECAPed Mg–Zn–Ca–Mn alloy has great potential for biomedical applications and a mechanism was proposed to explain the interrelations between the thermomechanical processing and bio-corrosion behavior.