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The porous hydroxyapatite coatings with a spherical structure were formed on commercially pure titanium (CP-Ti) by the micro-arc oxidation (MAO) in an alkaline electrolyte (hydroxyapatite + 1 M potassium hydroxide) at the applied voltage of 140, 160, 180 V and deposition time of 1 and 2 min. It was determined that by increasing voltage from 140 to 160 V the Ca/P ratio increases from 1.54 to 1.69, i.e., the composition of hydroxyapatite (HA) approaches to the biological one that accelerates formation of the interfacial bond between the implant and bone tissue. It was shown that increasing deposition time from 1 to 2 min at the voltage of 140 V promotes increasing Ca/P ratio. The corrosion resistance of CP-Ti with HA coatings was studied in Ringer's solution at a temperature of 37 °C. The best corrosion protection was observed for the coating deposited at 160 V, 1 min, when the thickness of the coating and HA formation is the highest. [ABSTRACT FROM AUTHOR]

The possibility of increasing the hardness to 1420 HV and the corrosion resistance of the CP-Ti surface using a combined plasma electrolytic treatment consisting in anodic plasma electrolytic nitrocarburising in a solution of ammonia, acetone and ammonium chloride at 900 °C and subsequent plasma electrolytic polishing is shown. The morphology, surface roughness, phase composition, structure and microhardness of the modified layer were studied. The corrosion characteristics of the treated surface were studied through potentiodynamic tests and electrochemical impedance spectroscopy. It has been shown that an increase in the surface roughness has a negative effect on the corrosion resistance. The proposed plasma electrolytic polishing makes it possible to remove the outer porous oxide layer, providing increased corrosion resistance. The highest reduction in the corrosion current density, by 13 times compared to CP-Ti and by two orders compared to a plasma electrolytic nitrocarburising sample, is achieved after plasma electrolytic polishing in a solution of ammonium fluoride (4%) at 300 V for 3 min. [ABSTRACT FROM AUTHOR]

The TA1 welded joints with different heat inputs were obtained by a fiber laser and their microstructure, mechanical properties and corrosion resistance in simulated saliva solution were studied. The results show that the microstructure in fusion zone (FZ) is needle-like α′ martensite and lath-shape α′ martensite, and that of the heat-affected zone (HAZ) is zigzag α phase. With the increase of heat input, the volume fraction of needle-like α′ martensite decrease and the microstructure is coarsened in FZ, but there is almost no change in the microstructure of the HAZ. The order of the corrosion resistance of welded joints with different heat inputs is the same as FZ > HAZ > base material (BM), and the heat input has a more influence on the corrosion resistance of FZ. The binary multiple linear regression relationship between the corrosion current density/charge transfer resistance and the length/width of α′ martensite was established, indicating that the width of α′ martensite is the main factor affecting the corrosion resistance. [ABSTRACT FROM AUTHOR]

The present work is aimed at developing corrosion-resistant biocompatible coatings on Cp-Ti by anodisation. The coatings were developed by anodising Cp-Ti at a voltage of 60 V over a period of 60 minutes. The coatings were developed by using two different electrolytes, namely ethylene glycol solution of NH4F and an aqueous solution of H3PO4. The developed coatings were annealed at 400 °C. The wettability, surface morphology and phase composition of the samples were evaluated by contact angle goniometry, field emission-scanning electron microscopy (FE-SEM) and X-ray diffractometry (XRD), respectively. The corrosion characteristics of th samples were analysed by potentiodynamic polarisation (PDP) and electrochemical impedance spectroscopy (EIS) in Kokubo's simulated body fluid (SBF) environment to resemble the human blood plasma. Anodisation of the Cp-Ti resulted in the formation of nanoporous structure, which on annealing, resulted in the dwindling of the nanopores. The anodised (A and B) and annealed samples (AH and BH) exhibited better hydrophilic surfaces with enhanced corrosion resistance as indicated by the decrease in current densities of A, AH, B and BH samples by 70.6%, 84.2%, 87.4% and 94.2%, respectively, compared to the substrate, which qualifies them to be corrosion resistant and biocompatible. [ABSTRACT FROM AUTHOR]

The TA1 welded joints with different heat inputs were obtained by a fiber laser and their microstructure, mechanical properties and corrosion resistance in simulated saliva solution were studied. The results show that the microstructure in fusion zone (FZ) is needle-like α′ martensite and lath-shape α′ martensite, and that of the heat-affected zone (HAZ) is zigzag α phase. With the increase of heat input, the volume fraction of needle-like α′ martensite decrease and the microstructure is coarsened in FZ, but there is almost no change in the microstructure of the HAZ. The order of the corrosion resistance of welded joints with different heat inputs is the same as FZ > HAZ > base material (BM), and the heat input has a more influence on the corrosion resistance of FZ. The binary multiple linear regression relationship between the corrosion current density/charge transfer resistance and the length/width of α′ martensite was established, indicating that the width of α′ martensite is the main factor affecting the corrosion resistance.

In this study, the electrochemical corrosion properties of commercial pure titanium (Cp-Ti) samples produced by additive manufacturing and forging were compared by plasma oxidizing. Plasma oxidizing processes were carried out at temperatures of 650 °C and 750 °C for 1 h and 4 h. Electrochemical corrosion experiments were carried out in Simulated Body Fluid (SBF) using open circuit potential, cyclic potentiodynamic polarization and electrochemical impedance spectroscopy methods. It was found that the coating thickness of F 750 °C-4 h and S 750 °C-4 h samples was the highest. The corrosion resistance of the samples produced by additive manufacturing is lower than that produced by forging due to the Lack of fusion (LOF) effect. The barrier layer developed by the plasma oxidizing process significantly improved the corrosion performance of additive manufacturing by reducing the LOF effect. The minimum corrosion rate was obtained at S 750°-4 h. While the total material loss due to corrosion was the lowest on this surface, the last corroded surface was F 750°-4 h. The maximum resistance was observed on the plasma oxidized surfaces for the group produced by forging. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the structural, tribological and electrochemical properties of Ag2O, ZnO, NiO coatings and Ag2O/ZnO/NiO nanocomposite films deposited on commercially pure titanium. Design/methodology/approach: Ceramic thin films (Ag2O, ZnO, NiO coatings and Ag2O/ZnO/NiO nanocomposite film) were deposited on commercially pure titanium (CP-Ti) substrate. Surface characterization of the uncoated and coated samples was made by structural surveys (scanning electron microscopic examinations and X-ray diffraction analyses), hardness measurements, tribological and corrosion experiments. Findings: Results were indicated that sol-gel coatings improved the wear and corrosion resistance of CP-Ti, and the best results were seen at the nanocomposite coating. It may be attributed to its small grain size, high surface hardness and high film thickness. Originality/value: This study can be a practical reference and offers insight into the influence of nanocomposite ceramic films on the increase of hardness, tribological and corrosion performance. Also, the paper displayed a promising approach to produce Ag2O/ZnO/NiO nanocomposite coating on commercially pure titanium implants for biomedical applications. [ABSTRACT FROM AUTHOR]

Phosphorus-incorporated oxide layers were grown on commercially pure titanium during plasma electrolytic oxidation in sodium dihydrogen phosphate dihydrate solution. Microstructure, mechanical and electrochemical behavior of the surface oxides indicated a dominant anatase and rutile structure of TiO 2 with nanocrystallites ranging from 45 to 64 nm and 48–98 nm, respectively as well as Ti2+, Ti3+ and Ti4+ chemical species. Using a combination of process time, applied current and electrolyte concentration, coating thicknesses up to about 10 μm were fabricated. Best mechanical performance was observed for potentiostatic deposited samples yielding a 453 HV 300 hardness, 19 N adhesive failure and 38 N full delamination resistance. All PEO-coated samples in this work exhibit a corrosion current density with one order of magnitude lower than CP-Ti when subjected to Ringer's physiological solution. • Preparation of PEO oxide layers on CP-Ti in an acid electrolyte solution containing NaH 2 PO 4 ∙2H 2 O • Comparison of potentiostatic and galvanostatic regimes on mechanical properties and corrosion resistance of PEO coatings obtained in similar growth conditions • The effect of PEO process time and current intensity during potentiostatic and galvanostatic operation mode on composition, microstructure, mechanical properties and corrosion behavior of oxide coatings • Influence of electrolyte concentration in restricting the growth of anatase - the role of phosphorous incorporation [ABSTRACT FROM AUTHOR]

Commercially pure titanium (CP-Ti) was subjected to thermal oxidation at different temperatures and times for determining the optimum oxidation conditions to obtain the optimum corrosion resistance. The phase constituents of the samples were determined by X-ray diffraction (XRD), the morphology of the surface was observed by SEM, and the corrosion behavior was investigated using immersion test by exposing the samples in HCl solutions with a concentration of 37%. The results showed that Rutile TiO2 layer was formed on the surface of CP-Ti after thermal oxidation and the thickness of the TiO2 layer increased with the treating temperature. Meanwhile, it was found that the optimum corrosion resistance to HCl was obtained while oxidizing at 700℃ for 330min～500min.

Titania coating was produced on commercially pure titanium by a pulsed DC plasma electrolytic oxidation (PEO) process in an aqueous electrolyte containing 5 g/l trisodium orthophosphate and 2 g/l potassium hydroxide. Four different PEO coatings were fabricated with two different duty cycles (10% and 95%) and two different current frequencies (50 Hz and 1000 Hz) while maintaining a constant current density and process time of 150 mA/cm 2 and 8 min, respectively. The phase composition, roughness, thickness, surface morphology and cross-sectional microstructure of the coating were assessed using X-ray diffraction (XRD), optical profilometer, eddy current thickness gauge and scanning electron microscope (SEM). The scratch resistance of the coating was assessed by a scratch test. The corrosion behaviour of the coating was studied in a Kokubo 7.4 pH simulated body fluid (SBF) solution by open circuit potential (OCP) measurement, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) with equivalent circuit modelling and EIS curve fitting. Among the coatings, the coating produced at 10% duty–50 Hz frequency had a lower thickness, poor corrosion resistance (i corr , 1.9 × 10 − 4 mA/cm 2 ) and poor scratch resistance (L c , 15 N) while the coating produced at 95% duty–1000 Hz frequency showed higher corrosion resistance (i corr , 3.3 × 10 − 6 mA/cm 2 ), higher scratch resistance (L c , 26 N) and had a dense coating. The coating with highest corrosion resistance also showed good wettability (contact angle, 61 ± 3°) and apatite forming ability under bioactivity test. [ABSTRACT FROM AUTHOR]

The present investigation reports the effect of different electrolyte additives on in-vitro corrosion behavior of the plasma electrolytic oxidation (PEO) coatings formed on commercially pure titanium (Cp-Ti). PEO coatings were produced using a pulsed DC power source at a constant current density of 70 mA/cm 2 and a treatment time of 8 min. Different coatings were developed with different additives (sodium sulfate, Tris, di-ammonium hydrogen phosphate and ammonium acetate) added to a base electrolyte consisting of TSOP and KOH. PEO coatings were characterized for phase composition, elemental composition, surface and cross-sectional microstructure, corrosion behavior, apatite forming ability and osteoblast cell adhesion. The corrosion resistance of the developed oxide coatings was evaluated in a Kokubo simulated body fluid (SBF) by potentiodynamic polarization test and EIS study. The in-vitro bioactivity of all the PEO coatings and the untreated substrate was studied by soaking the samples in an SBF environment for 21 days. The TiO 2 layer formed in phosphate, sulfate and nitrite containing electrolyte highly enhances the apatite formation in SBF. An in-vitro cell adhesion test was performed on all coatings using human osteosarcoma cells for 48 h. SEM images of cell adhesion test showed that human osteosarcoma cells were well adhered and spread on all PEO treated samples. Among all the additives, Tris has provided higher corrosion resistance in the SBF environment with good apatite forming ability and osteoblast cell adhesion. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical and cellular behavior of commercially pure titanium (CP-Ti) with both ultrafine-grained (UFG) and coarse-grained (CG) microstructure was evaluated in this study. Equal channel angular pressing was used to produce the UFG structure titanium. Polarization and electrochemical impedance tests were carried out in a simulated body fluid (SBF) at 37°C. Cellular behaviors of samples were assessed using fibroblast cells. Results of the investigations illustrate the improvement of both corrosion and biological behavior of UFG CP-Ti in comparison with the CG counterpart. [Copyright &y& Elsevier]

In this study, the surface of commercially pure titanium (Cp-Ti) was covered by a 21–95 µm-thick aluminum oxide layer using plasma electrolytic oxidation. Coating characterization revealed the formation of nodular and granular α- and γ-Al2O3 phases with minor amounts of TiAl2O5 and Na2Ti4O9 which yielded a maximum 49.0 GPa hardness and 50 N adhesive critical load. The corrosion resistance behavior in 3.5 wt.% NaCl solution of all plasma electrolytic oxidation (PEO) coatings was found to be two orders of magnitude higher compared to bare Ti substrate. [ABSTRACT FROM AUTHOR]

Mixed titanium-aluminum oxide coatings were successfully grown on grade-2 commercially pure titanium substrates by using plasma electrolytic oxidation technique. The mechanical features and the resistance against corrosion were attributed to microstructural, morphological and surface changes resulting from different preparation conditions. The formation of bulk metal oxides consisting of a dominant TiAl 2 O 5 /Ti 2 Al 6 O 13 structure together with α-Al 2 O 3 and γ-Al 2 O 3 phases in the coatings accompanied by fully oxidized metal atoms on top of the surface showed a maximum 24.5 GPa hardness and 45 N adhesive critical load, respectively. Best corrosion performance of the coatings in 3.5% NaCl was found to be two orders of magnitude higher when compared to uncoated Ti. [Display omitted] • Preparation of PEO oxide layers on grade 2 CP-Ti by galvanostatic regime • Successfully grown titanium-aluminum mixed oxides on Ti substrates • Additional α-Al 2 O 3 and γ-Al 2 O 3 formation inside the coatings • Excellent adhesion and microhardness of coatings to the substrate • Superior corrosion resistance of PEO layers compared to pure Ti [ABSTRACT FROM AUTHOR]