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Pure titanium is a preferred material for medical applications due to its outstanding properties, and the fabrication of its surface microtexture proves to be an effective method for further improving its surface-related functional properties, albeit imposing high demands on the processing accuracy of surface microtexture. Currently, we investigate the fabrication of precise microtextures on pure titanium surfaces with different grid depths using precision-cutting methods, as well as assess its impact on surface wettability through a combination of experiments and finite element simulations. Specifically, a finite element model is established for pure titanium precision cutting, which can predict the surface formation behavior during the cutting process and further reveal its dependence on cutting parameters. Based on this, precision-cutting experiments were performed to explore the effect of cutting parameters on the morphology of microtextured pure titanium with which optimized cutting parameters for high-precision microtextures and uniform feature size were obtained. Subsequent surface wettability measurement experiments demonstrated from a macroscopic perspective that the increase in the grid depth of the microtexture increases the surface roughness, thereby enhancing the hydrophilicity. Corresponding fluid-solid coupling finite-element simulation is carried out to demonstrate from a microscopic perspective that the increase in the grid depth of the microtexture decreases the cohesive force inside the droplet, thereby enhancing the hydrophilicity.

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OBJECTIVE: The addition of reinforcement bars is a commonly used method to improve the fabrication trueness of selective laser melting removable partial denture alloy frameworks. However, the effects of different reinforcement bar designs on the trueness of the entire framework remain unclear. This study investigated the trueness of removable partial denture frameworks of pure titanium fabricated by selective laser melting under different reinforcement bar settings. METHOD: A virtual framework was designed based on the Kennedy Class I partially edentulous model using computer-aided design software. Frameworks with different reinforcement bar settings (Ti-A without reinforcement bar, Ti-B with a single horizontal bar joining the lingual bar, Ti-C with two more bars at the anterior region, Ti-D with another horizontal bar at the anterior region, and Ti-E with one more bar at the posterior region, n = 5) were printed using pure titanium powder using a direct metal laser melting machine. The fabricated frameworks were scanned, and their fabrication trueness was compared with the designed virtual framework using one-way ANOVA. RESULTS: The overall mean discrepancies for Ti-A, Ti-B, Ti-C, Ti-D, and Ti-E were 0.111, 0.047, 0.073, 0.068, and 0.047 mm, respectively. For the group of Ti-A set with no reinforcement bars, larger discrepancies were observed compared with the other four groups (P < .05). Groups Ti-B and Ti-E showed better trueness of the RPI clasps, rests, and distal ends (P < .05). CONCLUSIONS: Adding reinforcement bars improved the printing trueness of the pure titanium frameworks, and different settings resulted in various degrees of improvement. Setting a single reinforcement bar to join the lingual bar or an additional reinforcement bar at the distal end significantly enhanced the printing trueness of the RPI clasps, rests, and distal ends.

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Re-endothelialization has been recognized as a promising strategy to address the tissue hyperplasia and subsequent restenosis which are major complications associated with vascular implant/interventional titanium devices. However, the uncontrollable over-proliferation of smooth muscle cells (SMCs) limits the clinical application of numerous modified strategies. Herein, a novel modified strategy involving with a two-step anodic oxidation and annealing treatment was proposed to achieve rapid re-endothelialization function regulated by regular honeycomb nanotexture and specific anatase phase on the titanium surface. Theoretical calculation revealed that the presence of nanotexture reduced the polar component of surface energy, while the generation of anatase significantly enhanced the polar component and total surface energy. Meanwhile, the modified surface with regular nanotexture and anatase phase produced positive effect on the expression of CD31, VE-Cadherin and down-regulated α-SMA proteins expression, indicating excellent capacity of pro-endothelial regeneration and inhibition of SMCs proliferation and migration. One-month in vivo implantation in rabbit carotid arteries further confirmed that modified tube implant surface effectively accelerated confluent endothelial monolayer formation and promoted native-like endothelium tissue regeneration. By contrast, original titanium tube implant induced a disorganized tissue proliferation in the lumen with a high risk of restenosis. Collectively, this study opens us an alternative route to achieve the function that selectively promotes endothelial cells (ECs) growth and suppresses SMCs on the medical titanium surface, which has a great potential in facilitating re-endothelialization on the surface of blood-contacting titanium implant.

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This study investigates the impact of hard coatings on the fatigue properties of pure titanium. A specialized fatigue test which ensured machine equivalence was conducted to compare the fatigue behavior of coated and uncoated metals. The findings reveal that the application of coatings adversely affects the fatigue properties of pure titanium due to stress concentration from the coating, which accelerates fatigue crack propagation within the substrate material. Notably, zigzag fatigue cracks at the interface between the coating and substrate and multiple micro-cracks initiated within the coating are found.

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PURPOSE: This study aims to develop a numerical prediction method for the average and standard deviation values of the largely varied fatigue life of additively manufactured commercially pure titanium (CPTi grade 2) clasps. Accordingly, the proposed method is validated by applying it to clasps of different shapes. METHODS: The Smith-Watson-Topper (SWT) equation and finite element analysis (FEA) were used to predict the average fatigue life. The variability was expressed by a 95% reliability range envelope based on the experimentally determined standard deviation. RESULTS: When predicting the average fatigue life, the previously determined fatigue parameters implemented in the SWT equation were found to be useful after conducting fatigue tests using a displacement-controlled fatigue testing machine. The standard deviation with respect to stroke and fatigue life was determined for each clasp type to predict variability. The proposed prediction method effectively covered the experimental data. Subsequently, the prediction method was applied to clasps of different shapes and validated through fatigue tests using 22 specimens. Finally, the fracture surface was observed using scanning electron microscopy (SEM). Many manufacturing process-induced defects were observed; however, only the surface defects where the maximum tensile stress occurred were crucial. CONCLUSIONS: It was confirmed that the fatigue life of additively manufactured pure titanium parts is predictable before the manufacturing process considering its variability by performing only static elasto-plastic FEA. This outcome contributes to the quality assurance of patient-specific clasps without any experimental investigation, reducing total costs and response time.

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Pure titanium is gaining increasing interest due to its potential use in dental and orthopedic applications. Due to its relatively weak mechanical parameters, a limited number of components manufactured from pure titanium are available on the market. In order to improve the mechanical parameters of pure titanium, manufacturers use alloys containing cytotoxic vanadium and aluminum. This paper presents unique explosive hardening technology that can be used to strengthen pure titanium parameters. The analysis confirms that explosive induced α-ω martensitic transformation and crystallographic anisotropy occurred due to the explosive pressure. The mechanical properties related to residual stresses are very nonuniform. The corrosion properties of the explosive hardened pure titanium test do not change significantly compared to nonhardened titanium. The biocompatibility of all the analyzed samples was confirmed in several tests. The morphology of bone cells does not depend on the titanium surface phase composition and crystallographic orientation.

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The micro-arc oxidation process was used to apply a ceramic oxide coating on a pure titanium substrate using calcium acetate and sodium dihydrogen phosphate as an electrolyte. The influence of the current frequency and duty ratio on the surface morphology, phase composition, wear behavior, and corrosion resistance were analyzed by employing a scanning electron microscope, X-ray diffractometer, ball-on-disk apparatus, and potentiodynamic polarization, respectively. Analyses of the surface and cross-sectional morphologies revealed that the MAO films prepared via a low current frequency (100 Hz) and a high duty ratio (60%) had a lower porosity and were more compact. The medium (500 Hz) and high (1000 Hz) frequencies at the higher duty ratios presented with better wear resistance. The highest film thickness (11.25 µm) was achieved at 100 Hz and a 20% duty ratio. A negligible current density was observed when the frequency was fixed at 500 Hz and 1000 Hz and the duty cycle was 20%.

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Pure titanium is widely used in clinical implants, but its bioinert properties (poor strength and mediocre effect on bone healing) limit its use under load-bearing conditions. Modeling on the structure of collagen fibrils and specific nanocrystal plane arrangement of hydroxyapatite in the natural bone, a new type of titanium (Ti) with a highly aligned fibrous-grained (FG) microstructure is constructed. The improved attributes of FG Ti include high strength (≈950 MPa), outstanding affinity to new bone growth, and tight bone-implant contact. The bone-mimicking fibrous grains induce an aligned surface topological structure conducive to forming close contact with osteoblasts and promotes the expression of osteogenic genes. Concurrently, the predominant Ti(0002) crystal plane of FG Ti induces the formation of hydrophilic anatase titanium oxide layers, which accelerate biomineralization. In conclusion, this bioinspired FG Ti not only proves to show mechanical and bone-regenerative improvements but it also provides a new strategy for the future design of metallic biomaterials.

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PURPOSE: In this study, the fatigue properties of additively manufactured titanium clasps were compared with those of commercially pure titanium (CPTi) and Ti-6Al-4V (Ti64), manufactured using laser powder-bed fusion. METHODS: Fourteen specimens of each material were tested under the cyclic condition at 1 Hz with applied maximum strokes ranging from 0.2 to 0.5 mm, using a small stroke fatigue testing machine. A numerical approach using finite element analysis (FEA) was also developed to predict the fatigue life of the clasps. RESULTS: The results showed that although no significant differences were observed between the two materials when a stroke larger than 0.35 mm was applied, CPTi had a better fatigue life under a stroke smaller than 0.33 mm. The distributions of the maximum principal stress in the FEA and the fractured position in the experiment were in good agreement. CONCLUSIONS: Using a design of the clasp of the present study, the advantage of the CPTi clasp in its fatigue life under a stroke smaller than 0.33 mm was revealed experimentally. Furthermore, the numerical approach using FEA employing calibrated parameters for the Smith-Watson-Topper method are presented. Under the limitations of the aforementioned clasp design, the establishment of a numerical method enabled us to predict the fatigue life and ensure the quality of the design phase before manufacturing.

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The 'plainification of materials' has been conceptualized to promote the sustainable development of materials. This perspective, for the first time in the field of biomaterials, proposes and defines 'plain metallic biomaterials (PMBs)' with demonstrated research and application case studies of pure titanium with high strength and toughness, and biodegradable, fine-grained and high-purity magnesium. Then, after discussing the features, benefits and opportunities of PMBs, the challenges are analyzed from both technical and regulatory aspects. Regulatory perspectives on PMB-based medical devices are also provided for the benefit of future research, development and commercialization.

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INTRODUCTION: The longevity of dental implants is affected by the ability to avoid any hypersensitivity or corrosive reactions in the oral cavity. The aim of the current study was to evaluate the cytotoxic effect of commercially pure titanium (cpTi), silver-palladium (Ag-Pd), and nickel-chromium (Ni-Cr) on human gingival fibroblast (HGF). METHODS: The sample size used was 10 discs from each alloy used with dimensions of 4x3mm. The HGF was derived from healthy patients subjected to gingivectomy procedures. Of the specimens, 50% were incubated in artificial saliva and the other half in Dulbecco's Modified Eagle medium (DMEM). The extract of each alloy in both media was collected and applied on HGF. After 24 hours the morphology of the HGF cells was examined to detect any apoptosis or cell death. Also, cell viability was evaluated by the use of a 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Statistical analysis was performed using students' t-test and two-way ANOVA with a significance level of p<0.05. RESULTS: In the case of morphological examination of HGF and MTT assessment, only cpTi alloy specimens didn't display any cytotoxic effect. Ni-Cr was the most cytotoxic alloy of the three. Also, MTT activities of all three alloys were decreased when they were incubated in artificial saliva. CONCLUSION: cpTi exhibited the highest corrosion resistance in comparison to Ag-Pd and Ni-Cr alloys. Ag-Pd alloys showed acceptable resistance to corrosion that is due to the passivity effect. Also, artificial saliva increased the cytotoxic effect of the tested alloys more than DMEM.

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The present work dealt with the development of a protective and functional oxide layer via one-step plasma electrolytic oxidation (PEO) on pure titanium by employing highly concentrated aluminate solution in a short processing time. A compositional analysis showed that Al2TiO5 active compound was formed successfully by means of Al2O3 incorporation when TiO2 was spontaneously developed with the aid of plasma swarms. The electrochemical performance showed the protective and functional capabilities of the layer, which was attributed to the respective amounts of Al2O3 and Al2TiO5. Such capabilities were achieved in a short processing time, thus reducing the total production cost.

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OBJECTIVES: Metallic element release during implant placement can lead to mucositis and peri-implantitis. Here, using ex vivo porcine mandibles, the release of metallic elements into the surrounding bone with different material and geometrical designs was quantified. METHODS: Implants from BioHorizons® and Straumann® (Bone level, tapered/cylindrical, 3/4 mm body diameter, Ti-CP4/Ti-6Al-4V/Ti-15Zr) systems were used. Micro computed tomography and inductively coupled plasma optical emission spectroscopy was used to visualise and quantify metallic elements in bone, following acid digestion. Implant surfaces were examined with scanning electron microscopy and internalization of implant particles by human gingival fibroblasts (HGFs) and RAW 264.7 macrophages were demonstrated in vitro. RESULTS: Implants with wider body diameters resulted in higher metallic element release. Ti-6Al-4V implants released significantly more metallic elements in comparison to both Ti-CP4 and Ti-15Zr devices with similar design and dimensions. Tapered Ti-CP4 implants released less compared to those with cylindrical design. Al three types of particles were internalized by HGFs and RAW 264.7. SIGNIFICANCE: Ti-CP4 and Ti-15Zr appear to be more suitable materials, however, further studies are required to elucidate the biological effects of the fine particles and/or metallic species from dental implants. Authors would like to raise the awareness in the dental profession community that careful evaluation of the materials used in dental implants and the potential risks of the individual constituents of any alloy are needed. The potential cytotoxicity of Ti-6Al-4V implant particles should be highlighted. Further investigations on the biological effect of the fine particles or metallic species released from dental implants are also needed.

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Milling and selective laser melting (SLM) technology have become new options for removable partial denture (RPD) processing. However, whether milling and SLM technology has an impact on the properties of RPD remains unclear, which is also the aim of our study. To investigate the effects of milling and SLM technology on pure titanium, mechanical property, corrosion resistance, and anti-adherence of specimens were evaluated, and specimens processed by lost-wax casting were used as control. Compared with casting and milling groups, the SLM group showed enhanced Vickers hardness (402.1 ± 13.0 HV), tensile stress (694.4 ± 4.5 MPa), and larger electrochemical capacitance arc radius compared with casting and milling groups. A series of adhesion-related genes (Als1, Als3, and HWP1) of Candida albicans cultured on SLM specimens were upregulated for more than two times that of casting and milling groups. However, images from scanning electron microscopy and confocal laser scanning microscopy exhibited similar biofilm morphology and biomass of C. albicans on a titanium disk processed by casting, milling, and SLM. Dwindled water contact angle (64.7 ± 0.6°) and higher TiO2 constituents (40.82%) in the SLM group might lead to the incompatibility of genetic expression and biofilm generation. Our findings indicated that SLM is an ideal process to produce titanium dentures, providing a reference on the selection of processing technology for dentists.

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Thrombosis induced by blood-contacting medical devices is still a major clinical problem, resulting in some serious complications such as infarction, irreversible tissue damage, and even death. Therefore, seeking an effective and safe surface modification approach to improve the hemocompatibility of the material is still urgent. In this research, a novel and facile approach was proposed to fabricate a robust honeycomb nanostructure on medical pure titanium surface by two-step anodic oxidation, which effectively enhanced the physicochemical performance and hemocompatibility of the material. Especially, the honeycomb nanostructure that underwent annealing treatment at 500 °C (HN-Ti-500 °C) presented significant performance to suppress the coagulation cascade in the in vitro tests, the reason mainly ascribed to an overall repulsive interaction between the protein molecule related to thrombosis and material surface based on an extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory analysis. Furthermore, a vessel stent fabricated by HN-Ti-500 °C was implanted into the left carotid artery of rabbits for 1 month. The antithrombotic mechanism and biocompatibility of the modified surface were further verified. The results presented that no thrombus generated and adhered onto the inner surface of the modified stent, and no obvious disorder hyperplasia and inflammation were observed in the intima tissue of the vessel at the implantation site, which indicated that the modified surface could effectively decrease the risk of in-stent restenosis and thrombosis. This work offers a promising strategy for surface modification of blood-contacting medical titanium material to address the clinical complications associated with restenosis and thrombosis.

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In the present work, an attempt has been made to study the influence of process parameters of the wire electric discharge machining (WEDM) process on the machining characteristics. The commercially pure titanium is machined by WEDM using brass wire as an electrode. The input parameters in this work were pulse on-time (Aon), pulse off-time (Aoff), servo voltage (SV) and wire tension (WT). On the other hand, dimensional accuracy (DA), average surface roughness (Ra) and maximum surface roughness (Rz) were chosen as the response parameters. The empirical relations developed for response characteristics were solved collectively using Evaluation Based on Distance from Average Solution (EDAS) and Particle Swarm Optimization (PSO). The optimized setting for minimizing the surface irregularities while machining titanium alloy on WEDM is predicted as Aon: 8 µs; Aoff: 13 µs; SV: 45 V; and WT: 8 N. Moreover, the predicted solution at the optimized parametric settings came out as DA: 95%; Ra: 3.163 µm; Rz: 22.99 µm; WL: 0.0182 g; and DR: 0.1277 mm. The validation experiments at the optimized setting showed the close agreement between predicted and experimental values. The morphological study by scanning electron microscopy (SEM) at the optimized setting revealed a significant reduction in surface defects such as micro cracks, micro cavities, globules and sub-surfaces, etc. In a nutshell, the study justified the effectiveness of EDAS-PSO in efficiently predicting the results for machining of pure titanium (Grade 2) using the WEDM process.

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The effect of slippage during High Pressure Torsion (HPT) of technically pure Ti and pure Cu samples was investigated. The "joint torsion of the disk halves" method was used to evaluate the effect of slippage. It was shown that slippage starts already at the early stages of HPT. With a further increase in the number of revolutions n, the slippage effect increases, and no torsional deformation occurs after n = 5. The slippage effect is explained by analyzing the surface friction forces between the sample and the anvil. However, studies via TEM and XRD have shown that the structure of Ti samples after HPT at the investigated conditions is grinded to a nanocrystalline state. A structure is formed in Ti similar to that observed after HPT by other authors. The dislocation density increases with increasing HPT degree from n = 5 to n = 10 revolutions, despite slippage. Consequently, despite slippage at HPT at n ≥ 5, deformation still occurs. The following assumptions are made to explain the accumulated strain in the sample at HPT. It is assumed that the planes of the upper and lower anvil during HPT are at a slight inclination relative to each other. Computer modeling using the Deform 3D software package has shown that this leads to the accumulations of significant strain during HPT.

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Objective@# To evaluate the effect of heat treatment on the bonding strength of pure titanium formed by selective laser melting (SLM) and porcelain.@*Methods@#Ninety-six pure titanium specimens were laser machined to meet ISO 9693 standards. The specimens were divided into a heat treated group (A) and a nonheat treated group (B). According to the porcelain type, the specimens in groups A and B were divided into Super Ti22 (a), Titankeramik (b), and Triceram (c) groups. Then, according to sandblasting pressures of 0.25 MPa (1) and 0.45 MPa (2), they were further divided into Aa1, Aa2, Ab1, Ab2, Ac1, Ac2, Ba1, Ba2, Bb1, Bb2, Bc1, and Bc2 groups. The surface morphology and roughness of the sandblasted specimens were assessed using a laser scanning confocal microscope. After the porcelain was fused, the three-point bending titanium-porcelain bonding strength was tested. A stereomicroscope was used to characterize the titanium-porcelain interfaces and determine the mode of failure.@* Results@# The Vickers hardness of group A specimens (188.21 ± 11.94) was significantly lower than that of group B specimens (204.48 ± 6.32) HV (P<0.05). The roughness value in group A1 (2.90 ± 0.32) μm was significantly lower than that in group A2 (3.43 ± 0.43) μm (P<0.05). Specimens in group B1 (2.62 ± 0.08) μm were significantly smaller than those in group B2 (3.01 ± 0.06) μm (P<0.05). The bonding strength in group Aa1 was (33.75 ± 2.31) MPa, group Aa2 was (36.32 ± 1.44) MPa, group Ab1 was (39.82 ± 2.28) MPa, group Ab2 was (33.74 ± 1.53) MPa and group Ac2 was (38.63 ± 1.36) MPa, which was significantly higher than that in the corresponding groups Ba1 (29.65 ± 1.10) MPa, Ba2 (27.17 ± 2.24) MPa, Bb1 (27.29 ± 1.61) MPa, Bb2 (23.85 ± 0.97) MPa, and Bc2 (35.75 ± 1.93) MPa (P<0.05). With increasing sandblasting pressure, the bonding strength of the titanium ceramic in group Aa2 was significantly higher than in group Aa1, while that in group Ab2 was significantly lower than that in group Ab1 (P<0.05). In groups A, Bc1 and Bc2, the fracture model showed mixed failure, while in groups Ba1, Ba2, Bb1, and Bb2, the model showed interfacial failure.@* Conclusion @# The Vickers hardness of SLM titanium can be significantly reduced by heat treatment. SLM pure titanium after heat treatment is beneficial to combination of the three porcelain types and titanium. The titanium-porcelain bonding strength may be affected by sandblasting pressure.

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Additive manufacturing of metallic materials, a layer-wise manufacturing method, is currently gaining attention in the biomedical industry because of its capability to fabricate complex geometries including customized parts fitting to patient requirements. However, one of the major challenges hindering the full implementation of additively manufactured parts in safety-critical applications is their poor mechanical performance under cyclic loading. This study investigated both quasi-static bending properties (bending stiffness, bending structural stiffness, and bending strength) and bending fatigue properties of additively manufactured (AM) commercially pure titanium (CPTi) limited contact dynamic compression plate (LC-DCP) constructs based on ASTM International standard for metallic bone plates (ASTM F382). In addition, the effect of post surface treatment methods including single shot-peened (SP), dual shot-peened (DP), and chemically assisted surface enhancement (CASE) on bending fatigue performance was also evaluated. Results indicated that bending stiffness and bending structural stiffness of AM CPTi LC-DCPs are comparable to conventionally manufactured (CM) counterparts; however, the bending strength of AM CPTi LC-DCPs is lower than CM counterparts. While the fatigue strength of as-built AM CPTi LC-DCPs is lower compared to the CM counterparts, AM CPTi LC-DCPs after post surface treatments (SP, DP, and CASE) exhibit statistically comparable fatigue strength to the CM CPTi LC-DCPs.

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Microstructures and corrosion properties of pure titanium were characterized when iron was used as a grain refiner. The added Fe element acted as a strong grain refiner for pure titanium by forming ß Ti phase at grain boundaries, and 0.15 wt% Fe was revealed to be a sufficient amount to make the grain size of pure titanium below 20 µm, which was the requirement for the desired titanium cathode. However, corrosion resistance was decreased with the Fe amount added. From the open circuit potential (OCP) results, it was obvious that the TiO2 stability against the reducing acid environment was deteriorated with the Fe amount, which seemed to be the main reason for the decreased corrosion resistance. Electrochemical impedance spectroscopy (EIS) results showed that both the decrease in the compact oxide film's resistance (Rb) and the appearance of the outer porous film occurred as a result of the dissolution of the TiO2 layer, whose phenomena became more apparent as more Fe was added.