Uncoated 316L Stainless Steel Research Articles

Investigation of corrosion and wear performance of TiNbTaZr/Cr-Mo PVD coatings on 316L SS in Hanks's solution for improved biomedical applications

316L stainless steel is popular due to its strength, durability, and especially cost-effectiveness in biomedical implant applications. However, the primary drawback of those materials is damage by corrosion and wear over prolonged exposure to the body's physiological environment. Thus, surface modification or coatings are essential to mitigate the corrosion and wear sensitivity of 316L implant materials. In this study, the corrosion and wear performance of TiNbTaZr/Cr-Mo PVD coatings on 316L stainless steel (SS) for improved biomedical applications have been investigated comprehensively. The coatings were deposited using an RF magnetron sputtering PVD system, and their morphological, structural, and wettability properties were characterized through SEM-EDS, GI-XRD, and contact angle measurements. The coatings' hardness was compared by using the Knoop hardness method and their surface roughness was analyzed by using a profilometer. Electrochemical corrosion tests and wear studies were conducted in both dry and simulated body fluid (SBF) conditions. The results indicated that the coatings exhibited nano-sized grain structures with no instances of delamination or cracking and consisted of a stable β-phase. The hardness of the coatings was significantly higher than that of the uncoated 316L sample. Contact angle measurements showed improved hydrophilicity for both coatings compared to uncoated 316L SS. Furthermore, the TNTZ-Mo coating demonstrated superior corrosion resistance and reduced wear under SBF conditions, making it a promising material for biomedical applications.

Corrosion Resistance, Interfacial Contact Resistance, and Hydrophobicity of 316L Stainless Steel Bipolar Plates Coated with TiN/Amorphous Carbon Double Layer under Different Carbon Target Currents

To improve the corrosion, interfacial contact resistance, and hydrophobicity of bipolar plates used in proton-exchange membrane fuel cells, a series of TiN/amorphous carbon double-layer coatings was prepared on 316L stainless steel using magnetron sputtering. The structure of the amorphous carbon was controlled with different carbon target currents. The changed rules in the coating structure and performance under different carbon target currents were studied. Due to appropriate sputtering energy, an appropriate carbon target current reduced the grain boundary of the coating, resulting in a smoother surface, and increased the content of sp2 hybrid carbon. Compared with uncoated 316L stainless steel, the samples coated with amorphous carbon showed greatly improved corrosion resistance and conductivity. At a carbon target current of 5 A, low contact resistance and high corrosion resistance were achieved simultaneously. The significant improvement in corrosion resistance is attributed to the improvement in the quality of the coating surface. Due to the appropriate carbon target current increasing the content of sp2 hybrid carbon in the coating, the contact resistance of the coating was reduced. When the carbon target current was 5 A, the interfacial contact resistance of the sample was 3.9 mΩ·cm2, which is significantly lower than that of bare 316L stainless steel. After constant potential polarization testing, the coating still exhibited good conductivity.

Improving the electrochemical corrosion behavior of stainless steel (316L) through the deposition of tantalum-based thin films

Austenitic 316L stainless steel (SS) is commonly used as a biomaterial for human implant applications. However, its clinical uses are limited due to its relatively high corrosion rate in physiological conditions. Various surface modifications, including coatings, have been developed to enhance its performance. In this study, a thin layer of Tantalum (Ta) was applied to the surface of 316L stainless steel using a DC Magnetron Sputtering (DCMS) system; the thickness of the coating varied from 1.504 to 6.083 µm, achieved by deposition times ranging from 15 to 60 min. The aim was to examine the electrochemical corrosion characteristics of the uncoated 316L SS and the Ta-coated 316L SS, followed by Potentiodynamic Polarization (PDP), Electrochemical Impedance Spectroscopy, and Open Circuit Potential tests. These tests were conducted for 10 min, 60 min, and 90 min to assess their performance over time. The PDP measurements took place in a simulated body fluid (SBF) at a pH of 7.8 ± 0.25 and a temperature of 40 °C, with varying coating durations. The PDP test outcomes revealed that the Ta-coated 316L stainless steel exhibited enhanced resistance to corrosion compared to the uncoated 316L stainless steel sample. The efficacy of Ta coatings on the 316L stainless steel samples was assessed through several techniques, including Optical microscopes, Energy Dispersive X-ray Spectroscopy, Scanning Electron Microscopy, and X-ray Photoelectron Spectroscopy. The findings from SEM and EDS verified the successful application of the Ta coating onto the stainless steel. The composition of the surface oxide film of Ta, the substrate, and the thickness of the coating were determined using the XPS technique, which confirms the effectiveness of the Ta coating in safeguarding 316L stainless steel against electrochemical corrosion, particularly for biomedical applications.

In vitro biological responses of plasma nanocoatings for coronary stent applications.

In-stent restenosis and thrombosis remain to be long-term challenges in coronary stenting procedures. The objective of this study was to evaluate the in vitro biological responses of trimethylsilane (TMS) plasma nanocoatings modified with NH3 /O2 (2:1 molar ratio) plasma post-treatment (TMS + NH3 /O2 nanocoatings) on cobalt chromium (CoCr) alloy L605 coupons, L605 stents, and 316L stainless steel (SS) stents. Surface properties of the plasma nanocoatings with up to 2-year aging time were characterized by wettability assessment and x-ray photoelectron spectroscopy (XPS). It was found that TMS + NH3 /O2 nanocoatings had a surface composition of 41.21 ± 1.06 at% oxygen, 31.90 ± 1.08 at% silicon, and 24.12 ± 1.7 at% carbon, and very small but essential amount of 2.77 ± 0.18 at% nitrogen. Surface chemical stability of the plasma coatings was noted with persistent O/Si atomic ratio of 1.292-1.413 and N/Si atomic ratio of ~0.087 through 2 years. The in vitro biological responses of plasma nanocoatings were studied by evaluating the cell proliferation and migration of porcine coronary artery endothelial cells (PCAECs) and smooth muscle cells (PCASMCs). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay results revealed that, after 7-day incubation, TMS + NH3 /O2 nanocoatings maintained a similar level of PCAEC proliferation while showing a decrease in the viability of PCASMCs by 73 ± 19% as compared with uncoated L605 surfaces. Cell co-culture of PCAECs and PCASMCs results showed that, the cell ratio of PCAEC/PCASMC on TMS + NH3 /O2 nanocoating surfaces was 1.5-fold higher than that on uncoated L605 surfaces, indicating enhanced selectivity for promoting PCAEC growth. Migration test showed comparable PCAEC migration distance for uncoated L605 and TMS + NH3 /O2 nanocoatings. In contrast, PCASMC migration distance was reduced nearly 8.5-fold on TMS + NH3 /O2 nanocoating surfaces as compared to the uncoated L605 surfaces. Platelet adhesion test using porcine whole blood showed lower adhered platelets distribution (by 70 ± 16%), reduced clotting attachment (by 54 ± 12%), and less platelet activation on TMS + NH3 /O2 nanocoating surfaces as compared with the uncoated L605 controls. It was further found that, under shear stress conditions of simulated blood flow, TMS + NH3 /O2 nanocoating significantly inhibited platelet adhesion compared to the uncoated 316L SS stents and TMS nanocoated 316L SS stents. These results indicate that TMS + NH3 /O2 nanocoatings are very promising in preventing both restenosis and thrombosis for coronary stent applications.

Hybrid nanocomposite coatings from PEDOT and BN-TiO2 nanosheets: Enhanced invitro corrosion resistance, wettability and biocompatibility for biomedical applications

The aim of this study is to develop the polymer nanocomposite coatings based on conducting polymer and hexagonal boron nitride (BN) nanosheets to improve invitro corrosion resistance and biocompatibility of 316L stainless steel (SS) implants. To achieve the highly dispersible BN, the surface of BN was decorated with TiO2 nanoparticles (~25 nm) and then, the resultant BN-TiO2 nanosheets was incorporated into poly (3,4-ethylene dioxythiophene) (PEDOT) coatings. Surface and structural characterization results validated the formation of nanocomposite coatings with homogeneous distribution of BN-TiO2 as well the existing interaction between the BN-TiO2 and PEDOT matrix. Invitro corrosion analysis of coated 316L SS specimens in simulated body fluid corroborated that the value of corrosion current density (0.0248 μA/cm2) was two orders of magnitude with a lower corrosion rate of 1.4694 × 10−3 mmpy for PEDOT/BN-TiO2 nanocomposite coatings compared with the pure PEDOT. Uncoated 316L SS specimen showed water contact angle (WCA) value of 84.50°, whereas PEDOT/BN-TiO2 coatings displayed WCA value of about 20°, further inferring the positive role of BN-TiO2 in the PEDOT matrix. Invitro cell culture analysis on MG63 cells validated the enhanced biocompatibility of developed nanocomposite coatings. Among the studied samples, the PEDOT/10BN-TiO2 nanocomposite coatings demonstrated enhanced wettability, invitro corrosion resistance, and ability to facilitate osteoblast adhesion. The obtained results suggest that the developed nanocomposite coatings on 316L SS implants have the potential for use in orthopedic applications.

Wear and corrosion behaviour of Ti-based coating on biomedical implants

ABSTRACT Biomedical implants are immensely manoeuvered devices that fix various deformities and injuries on medical grounds. With an emergent exploration in this field by researchers, countless combinations of materials have been discovered that perks global mankind. The ultimate goal of this experimentation is to appraise the characteristics of wear and corrosion resistance of Ti–Co–Cr-coated 316L grade austenitic stainless steel (SS) in contrast with TiN-coated and uncoated 316L SS. A micro-abrasion test was conducted on every single sample at 3N, 5N and 7N loads and were characterized in accordance with weight loss, coefficient of friction, surface roughness, Scanning Electron Microscope (SEM) analysis, X-ray Diffraction pattern (XRD), Energy Dispersive X-Ray Analysis (EDAX), Fourier-transform infrared spectroscopy (FTIR) and corrosion resistance. The findings showed that Ti–Co–Cr-coated substrate at 3N load have good mechanical tolerance and offers admirable performance. The corrosion resistance of the specimens divulges the biocompatibility of Ti–Co–Cr as being more distinct because of the existence of titanium metal.

Characterization of Hydroxyapatite Coating on 316L Stainless Steel by Sol–Gel Technique

Biomaterials are used for developing implants and producing a part or facilitating a function of a human body in a safe, reliable, and economical manner. Sol–gel deposition is one of the best, simple and economical methods of surface modification. In the current work, hydroxyapatite Ca10(PO4)6(OH)2, a bioactive material, has been prepared and then deposited on 316L stainless steel by the sol-gel coating method. The porosity percentage of hydroxyapatite coating was found to be 0.22. Electrochemical corrosion testing was carried out for both uncoated and sol-gel coated specimens. The coated specimens were characterized by the X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and cross-sectional analysis. The results revealed that the Ca/P ratio of the sol-gel coated steel was closer to that of a real human bone. It was found that hydroxyapatite-coated samples show better corrosion resistance and better implant properties as compared to those of the uncoated 316L stainless steel.

TRIBOLOGICAL BEHAVIOR OF THIN NANO TUNGSTEN CARBIDE FILM DEPOSITED ON 316L STAINLESS STEEL SURFACE

This study presents the tribological behavior of austenitic 316L Stainless Steel (SS) coated with nano Tungsten Carbide (WC). The nano WC particles were prepared by mechano chemical method. The tungsten and toluene have been ball milled for 40[Formula: see text]h led to the synthesis of WC nano particles. An average particles size of 48[Formula: see text]nm was achieved. The prepared nano WC particles were deposited on 316L SS substrate as a thin film using DC magnetron sputtering process. The thickness of the nano WC coating was 5[Formula: see text][Formula: see text]m. The synthesized nano WC particles and the thin nano WC film are characterized using Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and Energy Dispersive X-ray Analysis (EDAX) technique. Vickers microhardness test was conducted to evaluate the microhardness of the thin film. A high microhardness value of 2242 HV[Formula: see text] was observed. The coated specimens are subjected to wear test using pin on disc setup and the tribological parameters such as friction and wear are analyzed. The results were compared with uncoated 316L SS specimen and micro WC particles coated 316L SS. The nano WC coated 316L SS possess high hardness and better wear resistance when compared with 316L SS and micro WC coated 316L SS specimen.

Antimicrobial and biocorrosion-resistant MoO3-SiO2 nanocomposite coating prepared by double cathode glow discharge technique

In this investigation, a MoO3-SiO2 nanocomposite coating was developed on a 316L stainless steel (SS) substrate by double-cathode glow discharge deposition. Chemical valence states, phase composition and microstructure features of the nanocomposite coating were studied using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the nanocomposite coating was composed of a mixture of crystalline MoO3 and amorphous phases, in which amorphous SiO2 phase was embedded between the hexagonal-structured MoO3 grains with an average grain size of ∼8.4 nm. Nanoindentation and scratch tests, together with SEM and TEM observation of locally deformed regions, indicated that the nanocomposite coating exhibited high load-bearing capacity due to a combination of high hardness and good adhesion. Contact angle measurements suggested that the nanocomposite coating was more hydrophobic than uncoated 316L SS. The anti-bacterial activity of the MoO3-SiO2 nanocomposite coating against two bacterial strains (E. coli and S. aureus) was determined by the spread plate method. This showed that both bacterial strains exposed to the coating suffered a significant loss of viability. The influences of sulfate-reducing bacteria (SRB) on the electrochemical behavior of the MoO3-SiO2 nanocomposite coating in modified Postgate’s C seawater (PCS) medium were investigated through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The electrochemical tests revealed that the coating had a greater resistance to microbiologically influenced corrosion induced by SRB than uncoated 316L SS. This was corroborated by electrochemical testing (potentiodynamic polarization and EIS), in conjunction with SEM observations of the corroded surfaces.

Attenuation of the in vitro neurotoxicity of 316L SS by graphene oxide surface coating

A persistent theme in biomaterials research comprises of surface engineering and modification of bare metallic substrates for improved cellular response and biocompatibility. Graphene Oxide (GO), a derivative of graphene, has outstanding chemical and mechanical properties; its large surface to volume ratio, ease of surface modification and processing make GO an attractive coating material. GO-coatings have been extensively studied as biosensors. Further owing to its surface nano-architecture, GO-coated surfaces promote cell adhesion and growth, making it suitable for tissue engineering applications. The need to improve the long-term durability and therapeutic effectiveness of commercially available bare 316L stainless steel (SS) surfaces led us to adopt a polymer-free approach which is cost-effective and scalable. GO was immobilized on to 316L SS utilizing amide linkage, to generate a strongly adherent uniform coating with surface roughness. GO-coated 316L SS surfaces showed increased hydrophilicity and biocompatibility with SHSY-5Y neuronal cells, which proliferated well and showed decreased reactive oxygen species (ROS) expression. In contrast, cells did not adhere to bare uncoated 316L SS meshes nor maintain viability when cultured in the vicinity of bare meshes. Therefore the combination of the improved surface properties and biocompatibility implies that GO-coating can be utilized to overcome pertinent limitations of bare metallic 316L SS implant surfaces, especially SS neural electrodes. Also, the procedure for making GO-based protective coatings can be applied to numerous other implants where the development of such protective films is necessary.

Characterization of mechanical properties and electrochemical behaviour in a Hank´s solution of 316L/Cr1- xAlxN system

Cr1-xAlxN hard coatings were successfully deposited by R.F. reactive magnetron co-sputtering in an Ar/N2 gas mixture using chromium and aluminium targets on 316L stainless steel substrates. Crystallographic orientations associated to the Cr1-xAlxN FCC based in the conjugate complex of CrN and w-AlN phases, with ao=4.18Å lattice parameter for the ternary Cr1-xAlxN compound were identified by X-Ray diffraction. The thickness and roughness of the deposited coatings are 1.00±0.05nm and 2.65±0.6nm, respectively. The mechanical properties were determined by nanoindentation leading to a hardness of 27.8±2.6GPa and elastic modulus of 346GPa. The corrosion resistance of the coated 316L/Cr1-xAlxN system under simulated body fluid (SBF, Hank’s solution) was determined via electrochemical impedance spectroscopy. A reduction in the corrosion rate of 99% in relation to uncoated 316L stainless steel substrate was found by Tafel. Thus, these coatings seem to be excellent candidates to be used in biomedical applications.

Corrosion, haemocompatibility and bacterial adhesion behaviour of TiZrN-coated 316L SS for bioimplants

TiZrN coating was deposited on 316L stainless steel (SS) by the reactive magnetron co-sputtering technique. Cubic phase of TiZrN with uniform surface morphology was observed by X-ray diffraction and atomic force microscopy. Bacterial adhesion, haemocompatibility and corrosion behaviour of TiZrN coating were examined in order to evaluate the coating’s compatibility for ideal implant. Results revealed that TiZrN coatings exhibited less bacterial attachment against Staphylococcus aureus and Escherichia coli bacteria, negligible platelets activation and superior corrosion resistance than the uncoated 316L SS.

Towards more representative test methods for corrosion resistance of PEMFC metallic bipolar plates

Metallic bipolar plates are of increasing interest to automotive polymer electrolyte membrane fuel cell (PEMFC) manufacturers due to their low cost, high power density, ease of manufacture, high conductivity and good mechanical properties but minimising the undesirable effects of corrosion remains a key challenge. Unfortunately, reliable assessment of the applicability of stainless steels with a range of coatings and surface treatments has been hampered by a lack of representative ex situ test methods. Here we characterise the local environment experienced by a bipolar plate during fuel cell operation via in situ measurement of pH and corrosion potential for an uncoated 316L stainless steel bipolar plate in a single cell PEMFC. We demonstrate that the degradation mode is more akin to corrosion in relatively dilute thin liquid layers, rather than the fully immersed conditions employed in conventional ex situ screening tests. A key observation is that the corrosion potential of the bipolar plate is only weakly coupled to the potential of the nearest Pt electrode due to the low ionic conductivity of the discontinuous aqueous phase in the gas diffusion layer (GDL). However, localised polarisation of the steel can occur in the presence of oxygen as a result of galvanic coupling with the carbon GDL at wetted interfaces, a process which may be enhanced by the creviced geometry. The implications for development of more representative ex situ test protocols are discussed.

High-Temperature Oxidation Resistance of a Nanoceria Spray-Coated 316L Stainless Steel Under Short-Term Air Exposure

Nanoceria coatings using a spray method were implemented on a 316L stainless steel (SS). Coated and uncoated coupons were exposed to dry air at 1073 K to 1273 K (800 °C to 1000 °C) for short time periods (up to 24 hours) and in situ measurements of oxidation were carried out using a highly sensitive thermogravimetric balance. From the experimental outcome, activation energies were determined in both, coated and uncoated 316 SS coupons. The estimated exhibited activation energies for oxidation in the coated and uncoated conditions were 174 and 356 kJ/mol, respectively. In addition, the developed scales were significantly different. In the coated steel, the dominant oxide was an oxide spinel (Fe, Mn)3O4 and the presence of Fe2O3 was sharply reduced, particularly at 1273 K (1000 °C). In contrast, no spinel was found in the uncoated 316L SS, and Fe2O3 was always present in the scale at all the investigated oxidation temperatures. The coated steels developed a highly adherent fine-grained scale structure. Apparently, the nanoceria particles enhanced nucleation of the newly formed scale while restricting coarsening. Coarse grain structures were found in the uncoated steels with scale growth occurring at grain ledges. Moreover, the oxidation rates for the coated 316L SS were at least an order of magnitude lower than those exhibited by the steel in the uncoated condition. The reduction in oxidation rates is attributed to a shift in the oxidation mechanism from outward cation diffusion to inward oxygen diffusion.

Application of Taguchi Method for Characterization of Corrosion Behavior of TiO2 Coating Prepared by Sol‐Gel Dipping Technique

Titanium oxide (TiO2) nanoparticle coatings were deposited on the 316L stainless steel substrates by sol‐gel method. The morphology, structure, and corrosion resistance of the coating were analyzed using SEM, AFM, X‐ray diffraction, and electrochemical techniques. The deposition parameters employed to realize the anticorrosion performance including calcinations temperature, polyethylene glycol (PEG) content, pH value, and number of dipping cycles were investigated. Taguchi statistical experiments were carried out to determine the influence of the deposition variables on anticorrosion properties and optimal conditions. The results indicated that a higher anticorrosion performance of TiO2 films could be achieved using 1 g of PEG in a sol with pH in range of 7–9, six cycles of dipping, and calcination temperature at 400°C. The Tafel polarization measurements indicate that icorr value decreases about 200 times and the Rcorr value increases around 57 times compared with uncoated 316L stainless steel.

Microstructure and deuterium permeation resistance of the oxide scale prepared by initial oxidation method on vacuum solar receiver

Deuterium permeation resistant scales on vacuum solar receiver were developed by initial oxidation method. The initial oxidation atmosphere was produced by the H2–H2O mixtures at 827°C, with a low oxygen partial pressure of about 10−19Pa. The phases and morphologies of the oxide scales were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), X photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The formation of an oxide scale was observed with an inner layer essentially composed of chromium oxide and an outer layer mainly consisting of Mn1.5Cr1.5O4 spinels. The deuterium permeation of 316L stainless steel coated with Cr2O3 scale was only 1/80 of that of uncoated 316L stainless steel under loading of 80KPa at 600°C. The chromium oxide developed on the surface of 316L stainless steel revealed a marked inhibiting effect on the permeability of the deuterium and the associated mechanisms were discussed.

Development of Silica Glass Coatings on 316L SS and Evaluation of its Corrosion Resistance Behavior in Ringer’s Solution

Sol-gel derived silica glasses have many promising features, including low-temperature preparation as well as chemical and physical stability. Two silica glasses with Si100 and Si80 composition were prepared to understand the factors contributing to the rate of bioactivity. The effects of pH, solution aging temperature, and molar ratio of H2O/tetraethyl orthosilicate (TEOS) were studied, and the obtained powder sample was characterized by Fourier transform infrared spectroscopy, X-ray diffraction studies, and scanning electron microscopy. The synthesized silica glasses were deposited on 316L SS by the spin coating method at the optimized speed of 2000 revolutions per minute. The corrosion resistance behavior of the coatings was determined by (1) open-circuit potential vs time of exposure, (2) electrochemical impedance spectroscopy, and (3) cyclic polarization in Ringer’s solution. A higher breakdown potential (E b) and repassivation potential (E p) value with lower current density was obtained from cyclic polarization. Similar results were observed from impedance analysis with higher charge transfer resistance (R ct) and lower double layer capacitance (C dl) indicating the corrosion resistance behavior of the coatings compared with the uncoated 316L stainless steel. From the results, it was observed that both Si100 and Si80 glass coatings had a positive effect on the corrosion resistance behavior. An adhesive strength of 46 MPa and 45 MPa was obtained for the Si100 and Si80 coatings, respectively. An accelerated leach out study was carried out by impressing the potential at their breakdown potential to determine the effect of glass coating for long-term contact between the implant and a normal biological medium.

A comparison of carbon coated and uncoated 316L stainless steel for using as bipolar plates in PEMFCs

Two kinds of carbon coated and uncoated 316L stainless steel are studied to use as bipolar plates in fuel cells. The results show that the conductive amorphous carbon film has a low corrosion rate in simulated PEMFC environment. Rather long term potentiostatic tests and SEM investigations indicate that carbon thin films can be a good candidate to use as bipolar plate.

In vitro electrochemical evaluation and phase purity of natural hydroxyapatite coating on medical grade 316L stainless steel

AbstractNatural hydroxyapatite (HA) has been electrophoretically deposited on the surface of medical grade 316L stainless steel (SS). Deposition was performed at various applied voltages of 30, 60, and 90 V for 3 min. After deposition the samples were dried at room temperature and sintered in a vacuum furnace (10−4–10−5 Torr) at 800 °C for 1 h. In vitro electrochemical studies were performed in the Hank's solution. The results showed that corrosion potential and breakdown potential of the coated samples shifted toward nobler potential compared with the uncoated 316L SS. Electrochemical impedance spectroscopy investigations revealed a higher polarization resistance, total impedance, and lower capacitance values for the coated samples compared to the bare one which indicated the improvement of corrosion resistance of the coated samples. The surface morphology of the samples was studied by a scanning electron microscope, and also phase purity and crystallinity of the coating material were investigated by X‐ray diffraction. Deposition at 60 V for 3 min was found to be an optimum coating condition which led to the uniform, continuous, and crack‐free coatings. The crystallinity of the coating materials was measured to be high, and quantitative analysis of the coatings after sintering showed some partial decomposition of natural HA to tricalcium phosphate.

Surface characterisation and electrochemical behaviour of porous titanium dioxide coated 316L stainless steel for orthopaedic applications

Porous titanium dioxide was coated on surgical grade 316L stainless steel (SS) and its role on the corrosion protection and enhanced biocompatibility of the materials was studied. X-ray diffraction analysis (XRD), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) were carried out to characterise the surface morphology and also to understand the structure of the as synthesised coating on the substrates. The corrosion behaviour of titanium dioxide coated samples in simulated body fluid was evaluated using polarisation and impedance spectroscopy studies. The results reveal that the titanium dioxide coated 316L SS exhibit a higher corrosion resistance than the uncoated 316L SS. The titanium dioxide coated surface is porous, uniform and also it acts as a barrier layer to metallic substrate and the porous titanium dioxide coating induces the formation of hydroxyapatite layer on the metal surface.