Corrosion behaviors of hydroxyapatite coated by electrodeposition method of Ti6Al4V, Ti and AISI 316L SS substrates

Electrodeposition method was used to obtain hydroxyapatite (HAP) coatings on Ti6Al4V, Ti and AISI 316L SS substrates. Electrodeposition solution is prepared as Ca(NO₃)₂ · 4H₂O and (NH₄)H₂PO₄. Additionally, three different pretreatment surface operations (PTSO) (HNO₃, anodic polarization, baseacid) were applied to the substrates. Surface morphology of HAP coated substrates were characterized by SEM, EDS, XRD. HAP coatings were successfully deposited on Ti6Al4V, AISI 316L SS and Ti substrates Corrosion behavior of uncoated and HAP coated substrates were examined in the Ringer and 0.9% NaCl solutions. The XRD, SEM-EDS results supported that HAP formation on the substrates. i _cor values for all three HAP coated substrates are higher than uncoated substrates This showed that, electrochemical deposition HAP coating could not prevent the corrosion. The lowest corrosion rates were founded HNO₃ PTSO substrates.     

Preparation and characterisation of electrophoretically deposited hydroxyapatite coatings on type 316L stainless steel

Hydroxyapatite (HAP) coatings were developed on type 316L stainless steel (SS) by electrophoretic deposition at various deposition potentials from 30 to 90 V using the stoichiometric HAP (Ca/P ratio 1.67) powder in a suspension of isopropyl alcohol. The optimum coating parameters were established at 60 V and 3 min, after vacuum sintering at 800 °C. The phase purity of the coated surface was confirmed by XRD and secondary ion mass spectrometry confirmed the presence of both Ca and P on the coated layers. The electrochemical corrosion parameters E_corr (open circuit potential) and pitting potentials, evaluated in Hank’s solution shifted towards noble direction for the HAP coated specimens in comparison with uncoated type 316L SS. Electrochemical impedance spectroscopic investigations revealed higher polarisation resistance and lower capacitance values after immersing the coated specimens in Hanks solution for 200 h. This indicates the stable nature of the coatings formed.     

The Tribological Performance of Surface Treated Ti6A14V as Sliding Against Si<Subscript>3</Subscript>N<Subscript>4</Subscript> Ball and 316L Stainless Steel Cylinder

Closed field unbalanced magnetron sputtering was used to deposit diamond-like carbon (Ti-C:H) coatings on Ti6Al4V alloy and gas nitrided Ti6Al4V alloy. Four different specimens were prepared, namely untreated Ti6Al4V alloy (Ti6Al4V), gas nitrided Ti6Al4V alloy (N-Ti6Al4V), Ti-C:H-coated Ti6Al4V alloy (Ti-C:H/Ti6Al4V) and Ti-C:H-coated gas nitrided Ti6Al4V alloy (Ti-C:H/N-Ti6Al4V). The tribological properties of the four specimens were evaluated using a reciprocating wear tester sliding against a Si₃N₄ ball (point contact mode) and 316L stainless steel cylinder (line contact mode). The wear tests were performed in a 0.89 wt.% NaCl solution. The results showed that the nitriding treatment increased the surface roughness and hardness of the Ti6Al4V alloy and improved the wear resistance as a result. In addition, the Ti-C:H coating also improved the tribological performance of Ti6Al4V. For example, compared to the untreated Ti6Al4V sample, the Ti-C:H coating reduced the wear depth and friction coefficient by 340 times and 10 times, respectively, in the point contact wear mode, and 151 times and 9 times, respectively, in the line contact wear mode. It is thus inferred that diamond-like carbon coatings are of significant benefit in extending the service life of artificial biomedical implants.     

The Effect of Coating Thickness on Corrosion Resistance of Hydroxyapatite Coated Ti6Al4V and 316L SS Implants

Hydroxyapatite (HAP) has been coated onto Ti6Al4V and 316L SS substrates by sol-gel method. The coating thicknesses for the analysis were about 40 and 72 μm. Adhesion and corrosion tests have been conducted on uncoated and HAP-coated substrates. The coatings were characterized by XRD, SEM, and adhesion analysis. The corrosion resistance was examined in vitro by potentiodynamic polarization technique in Ringer’s solution at room temperature. Electrochemical analysis indicated that the highest corrosion susceptibility was found on 72-μm-coated 316L SS, and the 40-μm HAP-coated Ti6Al4V showed the highest corrosion resistance. It was observed that the coating thickness was an effective parameter on both adhesion and corrosion resistance. It was shown that adhesion and corrosion resistance decreased with increasing coating thickness on both substrates.     

Electrochemical corrosion of Ti6Al4V,Ti and AISI 316L SS after immersed in concentrated simulated body fluid

The biomimetic method is used to obtain hydroxyapatite (HAP) coatings on Ti6Al4V, Ti and AISI 316L SS substrates. These substrates with different pretreatment surface operations (HNO₃, anodic polarization, base-acid) were immersed in concentrated simulated body fluids (SBF) for different days at physiologic conditions of 37°C, initial pH of 7.4. Then the corrosion behaviours of substrates after immersion in concentrated SBF were examined by electrochemical methods in Ringer’s and 0.9 wt% NaCl solutions at a temperature of 37°C. Ions concentrations and pH analyses were carried out after incubation in concentrated SBF. After immersion in SBF for different days, the surface morphology remains almost unchanged and no apatite formation is observed. Corrosion currents of substrates increased after immersion. Ions concentrations and pH values were shown variability according to soaking time and pretreatment surface operations.     

Assessing the tribocorrosion performance of Ti–6Al–4V, 316 stainless steel and Monel K500 alloys in artificial seawater

The electrochemical and tribocorrosion behaviors of Ti–6Al–4V, 316 stainless steel and Monel K500 alloys sliding against Al₂O₃ in artificial seawater are investigated in this paper. It can be observed that the open circuit potential drops down to more negative values due to the removal of passive film. And a rapid dissolution occurs in the wear track compared with the unworn area. The wear loss polarized in cathodic potential is lower than that in anodic potential and open circuit potential conditions, because the material deterioration is enhanced by corrosive attack. The wear volumes of 316 stainless steel are much higher than the ones measured for Ti–6Al–4V and Monel K500 alloys. Friction coefficients are significant large in cathodic polarization compared with anodic polarization for all alloys. Moreover, the 316 stainless steel exhibits large friction coefficients compared with Ti–6Al–4V and Monel K500 alloys.     

Synthesis and high-temperature corrosion resistance of Ti-Zr-Si-N coatings deposited by means of sputtering

ABSTRACT

We present a study of the synthesis and an evaluation of the corrosion resistance of Ti-Zr-Si-N coatings deposited by means of the co-sputtering technique on 316L steel and Ti6Al4V alloy substrates. The thin films were obtained using Ti₅Si₂ and Zr targets with 99.9% purity for the deposition, and a power of 200 W was applied in the DC source and 170?W in the RF source. The corrosion resistance was evaluated via the cyclic oxidation test with consistent cycles of 1 hour of cooling, 1 hour of heating, and 16 minutes of stabilisation for 300 cycles at a temperature of 600°. The coatings were characterised by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and confocal laser microscopy. The coating was effective up to 150 cycles for the case of 316L steel, and up to 50 cycles for the Ti6AlV alloy.     

Production of Annealed Cold-Sprayed 316L Stainless Steel Coatings for Biomedical Applications and Their in-vitro Corrosion Response

316L powders were successfully deposited onto Al5052 aluminium substrates by cold spray method. Annealing was treated on the coated samples at 250–1000°C temperatures under Ar atmosphere. The in vitro performances of the coatings have been compared with using electrochemical corrosion test technique in the simulated body fluid (SBF) at body temperature (37°C). A scanning electron microscope (SEM-EDS) and X-ray diffraction (XRD) have been used for microstructural characterization and phases identifications of the coatings, respectively. The results were shown that there are high adhesions at particle and substrate interfaces and between the particles deposited as well. Also, the increasing annealing temperature increases corrosion resistance of the cold sprayed 316L stainless steel coatings. The corrosion susceptibility of the coating annealed at 1000°C was similar that of standard 316L stainless steel implant material in Ringer’s solution. The microstructural observations revealed that corrosion starts between the inter-splat powders and continues throughout the surface not in-depth.     

Pack Cementation Coatings for High-Temperature Oxidation Resistance of AISI 304 Stainless Steel

Aluminum and titanium are deposited on the surface of steel by the pack cementation method to improve its hot-corrosion and high-temperature oxidation resistance. In this research, coatings of aluminum and titanium and a two-step coating of aluminum and titanium were applied on an AISI 304 stainless steel substrate. The coating layers were examined by carrying out scanning electron microscopy (SEM) and x-ray diffraction (XRD). The SEM results showed that the aluminized coating consisted of two layers with a thickness of 450???m each, the titanized coating consisted of two layers with a thickness of 100???m each, and the two-step coatings of Al and Ti consisted of three layers with a thickness of 200???m each. The XRD investigation of the coatings showed that the aluminized coating consisted of Al₂O₃, AlCr₂, FeAl, and Fe₃Al phases; the titanized layers contained TiO₂, Ni₃Ti, FeNi, and Fe₂TiO₅ phases; and the two-step coating contained AlNi, Ti₃Al, and FeAl phases. The uncoated and coated specimens were subjected to isothermal oxidation at 1050?°C for 100?h. The oxidation results revealed that the application of a coating layer increased the oxidation resistance of the coated AISI 304 samples as opposed to the uncoated ones.     

Effects of Duplex Nitriding and TiN Coating Treatment on Wear Resistance,Corrosion Resistance and Biocompatibility of Ti6Al4V Alloy

Ti6Al4V alloy substrates were nitrided at 900 °C. TiN coatings were then deposited on the nitrided substrates using a closed-field unbalanced magnetron sputtering system. The microstructure, hardness and adhesion properties of the TiN-N-Ti6Al4V substrates were evaluated and compared with those of an untreated Ti6Al4V sample, a nitrided Ti6Al4V sample and a TiN-coated Ti6Al4V sample, respectively. The tribological properties of the various samples were investigated by means of reciprocating sliding wear tests performed in 0.9 wt.% NaCl solution against 316L, Si₃N₄ and Ti6Al4V balls, respectively. In addition, the corrosion resistance was evaluated using potentiodynamic polarization tests. Finally, the biocompatibility of the samples was investigated by observing the attachment and growth of purified mouse leukemic monocyte/macrophage cells (Raw 264.7) on the sample surface after culturing periods of 24, 72 and 120 h, respectively. Overall, the results showed that the duplex nitriding/TiN coating treatment significantly improved the tribological, anti-corrosion and biocompatibility properties of the original Ti6Al4V alloy.     

大气等离子喷涂TiB2-316L不锈钢基复合涂层及其耐磨性能

分别采用高能球磨制备了TiB2含量(质量分数)为10%的316L不锈钢基复合粉,高能球磨与喷雾干燥造粒工艺制备了TiB2含量(质量分数)为40%的316L不锈钢基复合粉,大气等离子喷涂制备相应的TiB2-316L不锈钢基金属陶瓷涂层与316L不锈钢涂层.室温下采用高速环块磨损试验研究TiB2-316L不锈钢基金属陶瓷涂层的磨损特性.采用X射线衍射分析涂层物相,扫描电镜分析喷涂粉末、涂层结构和摩擦副磨损表面形貌.结果表明,大气等离子喷涂两种制粉工艺获得的316L不锈钢基TiB2复合粉能获得较耐磨的316L不锈钢基TiB2复合涂层,耐磨性高于316L不锈钢涂层,且TiB2在复合涂层中增强涂层耐磨性的原因是TiB2颗粒在涂层316L韧性基体中充当强化相,且TiB2在摩擦接触处摩擦氧化形成的氧化产物具有自润滑特性,能减少涂层的磨损量.     

Corrosion behaviour of single and double layer hydroxyapatite coatings on 316L stainless steel by plasma spray

AISI316L stainless steel is extensively used in orthopedic and dental applications. However, this alloy exhibits low integration behaviour when it comes in contact with surrounding bone tissue and implant healing duration can be as much as few months. The aim of this study is the fabrication of biocompatible hydroxyapatite (HA) coatings on stainless steel substrate in order to accelerate the process of osseointegration of implants. The biocompatible single layer of Titania (TiO₂), Hydroxyapatite and bi-layer TiO₂/HA coatings were deposited by atmospheric plasma spray on 316L stainless steel. Coated and uncoated stainless steel specimens were incubated in simulated body fluids and 0.9% NaCl solutions for 1h and 7 days. In vitro electrochemical-corrosion evaluation of coated and uncoated stainless steel specimens have been investigated by Tafel extrapolation and linear polarization methods. Results indicates that corrosion resistance of single layer HA coated stainless steel specimens are superior to single layer TiO₂ and bi-layer HA/TiO₂ coated stainless steel specimens.     

Porous ceramic coating formed on 316L by laser cladding combined plasma electrolytic oxidation for biomedical application

In order to improve the bioactivity of 316L stainless steel, a titanium layer was prepared on the surface of 316L by laser cladding (LC), followed by plasma electrolytic oxidation (PEO) to form a porous ceramic coating on titanium layer. The morphologies, microstructure and compositions of the coated samples were characterized by 3D surface profiler, SEM, EDS, XRD and XPS. The corrosion resistance and bioactivity of the coatings were evaluated by potentiodynamic polarization and immersion test in simulated body fluid (SBF), respectively. The results showed that the porous ceramic coating mainly consisted of anatase and rutile, and highly crystalline HA was also detected. The main elements of the PEO coating are Ca, P, Ti and O. The LC+PEO composite bio-coating has more excellent corrosion resistance than the 316L substrate in simulated body fluid. Furthermore, the composite coating could effectively improve the bioactivity of 316L stainless steel.     

Characterization of Thermal-Sprayed HAP and HAP/TiO<Subscript>2</Subscript> Coatings for Biomedical Applications

In the present study, hydroxyapatite (HAP) coating along with HAP/TiO₂ coating has been deposited by high-velocity flame spray (HVFS) technique onto 316LSS. Titania was used as a bond coat and HAP as top coat in HAP/TiO₂ coating. The main aim of the study is to investigate the corrosion behavior of thermal spray coating of HAP and HAP/TiO₂ on steel. Electrochemical corrosion testing was carried out using potentiodynamic polarization test. The corrosion behavior of bare and as-sprayed specimens was analyzed in simulated body fluid known as Hank’s solution. As-sprayed specimens along with corroded specimens were further characterized by XRD, SEM/EDS, and x-ray mapping analysis. It was observed that the HAP/TiO₂ coating possessed higher microhardness (280 Hv) as compared to HAP coating (254 Hv). Surface roughness also got enhanced in case of HAP/TiO₂ coating (9.35 μm) as compared to pure HAP coating (7.37 μm). The porosity of the HAP coating was found to be higher than the bond coating. It was observed that the Ca/P ratio almost resembled that of the natural bone composition. The corrosion resistance of steel increased after the deposition of HAP and HAP/TiO₂ coatings. The maximum corrosion resistance was exhibited by HAP/TiO₂ coating.     

Corrosion behavior of TiN coated type 316 stainless steel in simulated PEMFC environments

The corrosion behavior of TiN coated type 316 stainless steel (SS) was investigated in simulated proton exchange membrane fuel cell environments, i.e. 0.01 M HCl + 0.01 M Na₂SO₄ solutions bubbled with pure oxygen and hydrogen gases, respectively, by using electrochemical measurement techniques. 316SS substrate can passivate spontaneously in simulated cathode environment, while it is in active state at the corrosion potential in simulated anode environment. TiN coatings have much better corrosion resistance and passivity under both simulated conditions. No significant degradation takes place in TiN coatings under the typical load conditions of fuel cell for 4 h. The loss of small part of coatings occurs during the immersion tests of TiN coatings in the oxygen environment for 1000 h and in the hydrogen environment for 240 h, respectively, but the exposed substrate areas are passivated in both environments. The results reveal that TiN coating can offer 316SS higher corrosion resistance and electric conductivity, and that further effort to improve the coating quality and to evaluate the long-term stability of 316SS/TiN coating systems under simulated conditions are deserved. In addition, the characteristics of corrosion process for TiN coatings on passivatable substrate were discussed in detail.     

A facile electrodeposition of hydroxyapatite onto borate passivated surgical grade stainless steel

This paper reports a successful electrodeposition method for coating hydroxyapatite (HAP) onto surgical grade stainless steel (SS). Pure HAP coatings could be achieved at −1400 mV vs SCE and the coating resistivity was assessed by potentiodynamic polarization and impedance techniques which showed that HAP coatings deposited onto the borate passivated-SS specimens possess maximum bioresistivity in Ringer’s solution. The coatings were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). The results have showed that the borate passivation followed by HAP coating performed on 316L SS could enhance the longevity of the alloy in Ringer’s solution.     

Microstructure and mechanical properties of CrN coating deposited by arc ion plating on Ti6Al4V substrate

CrN coatings have been grown by arc ion plating (AIP) onto Ti6Al4V alloy substrate at various nitrogen pressures (PN₂). The goals of this investigation are to study the influence of nitrogen pressure content on the composition, structure and mechanical properties of AIP CrN coatings, as well as their tribological properties. With an increase of PN₂, the main phases in the coatings changed from CrN + Cr₂N + Cr to CrN, and the texture of CrN was transformed from CrN (111)-oriented to (220)-oriented. Furthermore, the multi-layers including a metal Cr layer, a Cr₂N layer and a CrN layer were observed by cross-sectional TEM (XTEM), besides an “unbalanced” state transition layer at the interface of CrN/substrate which was analyzed by nucleation thermodynamics subsequently. An increase in nitrogen pressure also resulted in a change of micro-hardness due to the variation in composition and structure. Finally, the tribological properties of the Ti6Al4V substrate and the CrN/Ti6Al4V coating system have also been explored, which shows that CrN coatings can act as good wear resistance layer for Ti6Al4V substrate.     

人工模拟体液中pH值对离子注N人体医用合金腐蚀行为的影响

采用电化学测试技术研究了在人工模拟体液中pH值变化对离子注N人体用SUS316L不锈钢,Co-Cr合金,工业纯Ti和Ti-6Al-4V合金腐蚀行为的影响。结果表明,随着pH值的降低,试样的腐蚀电位负移,SUS316L不锈钢和Co-Cr合金的点蚀电位与缝隙腐蚀电位降低,使材料发生局部腐蚀的敏感性提高,工业纯Ti和Ti-6Al-4V合金的腐蚀电流密度增大,提高离子释放速度,加大对人体的潜在生理危害。     

Enhancing Biocompatibility and Corrosion Resistance of Ti-6Al-4V Alloy by Surface Modification Route

Titanium (Ti) and its alloys are widely used as candidate materials for biomedical implants. Despite their good biocompatibility and corrosion resistance, these materials suffer from corrosion after implantation in biological environments. The aim of this research work is to study the effect of two coatings on biocompatibility and corrosion behavior of Ti-6Al-4V biomedical implant material. Hydroxyapatite (HA) and hydroxyapatite/titanium dioxide (HA/TiO₂) coatings were thermal-sprayed on Ti-6Al-4V substrates. In the latter case, TiO₂ was used as a bond coat between the substrate and HA top coat. The corrosion behavior of coated and un-coated samples in Ringer’s solution was studied by potentiodynamic and linear polarization techniques. Before and after corrosion testing, XRD and SEM/EDS techniques were used for the analysis of phases formed and to investigate microstructure/compositional changes in the coated specimens. The cellular response was analyzed by the MTT (microculture tetrazolium) assay. The results showed that both the HA, as well as, the HA/TiO₂ coatings significantly increased the corrosion resistance of the substrate material. The HA coating was found to be more biocompatible as compared to the un-coated and HA/TiO₂-coated Ti-6Al-4V alloy.     

Corrosion behaviors of arc spraying single and double layer coatings in simulated Dagang soil solution

Three kinds of single layer coatings of Zn, Zn15Al, 316L stainless steel and two kinds of double layer coatings with inner layer of Zn or Zn15Al and outer layer of 316L stainless steel by arc spraying were developed to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against soil corrosion. The corrosion behaviors of the coated Q235 steel samples in the simulated Dagang soil solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and natural immersion tests. The results show that the corrosion of the matrix Q235 steel is effectively inhibited by Zn, Zn15Al, Zn+316L and Zn15Al+316L coatings. The corrosion rate value of Zn15Al coated samples is negative. The corrosion products on Zn and Zn15Al coated samples are compact and firm. The corrosion resistance indexes of both Zn and Zn15Al coated samples are improved significantly with corrosion time, and the latter are more outstanding than the former. But the corrosion resistance of 316L coated samples is decreased quickly with the increase in immersion time. When the coatings are sealed with epoxy resin, the corrosion resistance of the coatings will be enhanced significantly.