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Titanium Corrosion in Alkaline Hydrogen Peroxide
Abstract
Corrosion of ASTM Grade 2 Ti in alkaline peroxide environments was studied by a combination of experiments utilizing weight loss measurements, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarography. A corrosion mechanism was proposed, based on peroxide concentration and reaction of the oxide with the perhydroxyl ion (OOH-), that accounted for oxide dissolution or thickening, depending on the solution chemistry. It was found that hot alkaline peroxide solutions offer the possibility of acting as nonhydrogen-generating pickling solutions for industrial cleaning and preparation of Ti surfaces.
... There is much attention paid on the corrosion behavior of metallic Ti over H 2 O 2 , because it is important for harmless biomedical implantation and resistant pulp bleaching equipment [27][28][29]. It has been reported that amorphous hydrated titania porous film can be obtained via direct oxidation of metallic titanium plate with hydrogen peroxide [29]. ...
... It has been reported that amorphous hydrated titania porous film can be obtained via direct oxidation of metallic titanium plate with hydrogen peroxide [29]. And the corrosion oxidation rate can be enhanced when exposed to alkaline hydrogen peroxide [28]. In this contribution, by direct oxidation of metallic Ti with concentrated H 2 O 2 and NaOH for relatively short reaction times at low temperature, a nanowire film was fabricated on Ti plate surface. ...
... The mechanism of formation of titanate nanowires using TiO 2 as starting materials, by high temperature hydrothermal methods, has been discussed widely [31,39]. And the basic principle for Ti corrosion in alkaline H 2 O 2 solution has been discussed [28]. A dissolution and precipitation mechanism is proposed for the formation of the titania nanorod via direct oxidation of the Ti plate by H 2 O 2 [40][41][42]. ...
Photocatalytic anatase TiO2 nanowire thin films have been prepared by in situ oxidation of Ti plate in a mixture solution of concentrated H(2)O(2) and NaOH, followed by proton exchange and calcination. The morphologies and properties of the titanate and titania films have been investigated by means of field emission scanning electron microscopy, energy-dispersive x-ray spectrometry, high resolution transmission electron microscopy, x-ray diffraction and Raman spectrometry. The mechanism of formation of the porous microstructure has been discussed; it is the result of the balance between dissolution and precipitation. And sodium ions in the solution are needed to combine with titanate species for the nanowire formation. The anatase TiO2 nanowire thin films exhibited enhanced photocatalytic activity and stability in phenol degradation. The combination effects of the porous morphology and nanowire characteristics are favorable for improved photocatalytic performance. This novel nanowire film is promising for practical aqueous purification.
... It can be seen that, the MRRs of TC4 alloy with 100 mM H 2 O 2 , 100 mM K 2 S 2 O 8 and 25 mM KIO 4 are 103 nm −1 min −1 , 59 nm min −1 and 41 nm min −1 , respectively, implying that H 2 O 2 acts not only as an oxidizer but also another chemical role under alkaline conditions, such as complexing agent. 21 Surface film properties of TC4 alloy affected by the synergistic action of H 2 O 2 and K + under alkaline conditions.-The above polishing results confirm that, under alkaline conditions, the MRR of TC4 alloy can be significantly enhanced by the synergistic action of H 2 O 2 and K + . ...
... As shown in the electrochemical results, at alkaline pH, H 2 O 2 can greatly promote the corrosion of TC4 alloy through oxidation and complexation. The reactions can be depicted as follows, where n corresponds to either 1 or 2: 21 40 After adding K + , some K + ions are adsorbed on the Stern layer of the TC4 alloy surface and the silica particles. 41 On the one hand, the Stern layer of the TC4 alloy surface is enriched with K + ions, shielding the surface negative charge, 42 and as a result, the negatively charged OOH − and OH − can approach the surface easily, 15 leading to the enhanced corrosion as depicted in Eqs. 1 to 5, which is confirmed by the electrochemical results shown in Figs. 15 and 16. ...
Ti-6Al-4V (TC4) alloy has been widely used for implants, and excellent surface quality is required for satisfactory performance. In this study, chemical mechanical polishing (CMP) was introduced to process TC4 alloy. H2O2 and K+ were used to enhance the CMP efficiency. It is revealed that, at pH 10, the material removal rate (MRR) of TC4 alloy increases with the increasing H2O2. A synergistic action between H2O2 and K+ exists under alkaline conditions. With H2O2 and at pH 10, as the K+ concentration increases, the MRR of TC4 alloy first increases and then levels off. The anions have little influence on the CMP performance. After polishing, the surface is smooth without scratches, and the substrate underneath the surface film has no processing damage. For the synergistic action, K+ ions are adsorbed on the Stern layer of the TC4 alloy surface and the silica particles, screening the surface negative charge. Firstly, OOH- produced from H2O2 and OH- can approach the TC4 alloy surface easily, promoting the corrosion. Secondly, more silica particles come into contact with the TC4 alloy surface, enhancing the interactions. Therefore, the MRR increases. The research work brings about a promising high-efficiency CMP process for titanium alloys.
... Currently, interest in the application of titanium alloys to mechanical and tribological components is growing rapidly for a wide range of applications. However, titanium usage is restricted in practice due to its tribological behavior, characterized by high friction coefficients and high wear rates, and its limited corrosion resistance in some acid environments [4][5][6]. One approach to overcome this issue is to form a coating or surface layer on the base metal in order to modify its surface properties [7][8][9]. ...
... Fig . 1 shows the potential-time and current-time curves for the galvanostatic and potentiostatic anodizing in the three different electrolytes. The potential-time responses during galvanostatic anodizing ( Fig. 1a-b) show the characteristic behavior of plasma electrolytic oxidation [3,4,23]. First, the potential increases rapidly from 0 to 200 V due to the formation of a barrier layer, and then the slope of the curve decreases until the process reached~370 V, especially for the Na 2 WO 4 addition. ...
Spark anodizing of Ti6Al4V alloy has been performed in alkaline electrolytes containing aluminate to form wear-resistant coatings. Coatings obtained under potentiostatic conditions exhibit a better wear resistance, with a wear rate approx. 10 times lower than galvanostatic coatings, due to the formation of coatings with low porosity since potentiostatic mode controls the size of the micro-discharges. The coatings consist mainly of γ - Al2O3, whilst Al2TiO5 is present in minor proportions. For some coatings, the formation of Al6KO9.5 is observed due to the incorporation of potassium into the coating. EDS analysis shows that aluminum is the main constituent of the coatings, being mainly incorporated from the anodizing solution and homogeneously distributed into the coating. A decrease in pore density between 15 and 30% and roughness reduction of 10 to 60% was obtained with KOH and Na2WO4 additions, improving the coating wear resistance in pin-on-disc wear tests, especially by Na2WO4 addition.
... Glow discharge plasma deposition can get a clean surface, and the thickness of the oxide film obtained is 2 nm to 150 nm [2][3][4][5][6][7][8]. The oxide film obtained from oxygen ion implantation is thicker, about several microns [9][10][11][12][13][14]. Hydrogen peroxide treatment of titanium alloy surface is a process of chemical dissolution and oxidation [15,16]. The dense part of the oxide film is less than 5 nm [17][18][19][20][21]. ...
The biological activity, biocompatibility, and corrosion resistance of implants depend primarily on titanium dioxide (TiO2) film on biomedical titanium alloy (Ti6Al4V). This research is aimed at getting an ideal temperature range for forming a dense titanium dioxide (TiO2) film during titanium alloy cutting. This article is based on Gibbs free energy, entropy changes, and oxygen partial pressure equations to perform thermodynamic calculations on the oxidation reaction of titanium alloys, studies the oxidation reaction history of titanium alloys, and analyzes the formation conditions of titanium dioxide. The heat oxidation experiment was carried out. The chemical composition was analyzed with an energy dispersive spectrometer (EDS). The results revealed that titanium dioxide (TiO2) is the main reaction product on the surface below 900°C. Excellent porous oxidation films can be obtained between 670°C and 750°C, which is helpful to improve the bioactivity and osseointegration of implants.
1. Introduction
Titanium alloy is widely used as a biomaterial due to its superior biocompatibility, mechanical properties close to human bones, and enhanced corrosion resistance. These properties have made the alloys suitable for use in a wide spectrum of biomedical applications including artificial bones, artificial joints, dental roots, and medical devices. The excellent performance of titanium alloy is mainly due to the oxide film as shown in Figure 1 [1]. The functional composition of the oxide film is mainly titanium dioxide (TiO2). Titanium dioxide has good biocompatibility, stable chemical property, and low solubility in water, which prevents substrate metal ions from dissolution. Furthermore, it also improves the wear and fatigue resistance of implants in the human body.
... Very little is described in the literature about the peroxide etching mechanism. Corrosion of Ti in alkaline peroxide has been studied for the pulp industry which has led to some understanding of the reactions involved [44,45]. [46]. ...
Evaluation of the wet etching properties of several different thin film oxides grown by physical vapour deposition was performed in this work. were coated on two types of substrates; Si and borosilicate glass and etching tests were performed in different etching solutions. MgF 2 thin films have also been evaluated.
... The morphology change of sample (c) to that of sample (a) was in keeping with the formation of titanate nanowires from the sheets structure. Additionally, high temperature and high concentration of H 2 O 2 were conductive to the generation of netlike Na 2 Ti 3 O 7 [26]. So, both XRD and SEM observations presented the coincident results and showed that the short nanorods of sample (a) and the layered sheets of sample (c) were Na 2 Ti 3 O 7 . ...
Na2Ti3O7/titanium peroxide composites (TN-TP) were successfully prepared with the reaction of Ti foils, NaOH, and H2O2 at 60°C for 24 h in water bath. The Na2Ti3O7 appeared as nanorods in composites. Water bath temperature, water bath time, and the concentration of H2O2 and NaOH were crucial. The reaction mechanism was proposed. TN-TP was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric and differential scanning calorimetry (TG-DSC). TN-TP was a mesoporous material and exhibited stronger adsorption capability for neutral red (NR), malachite green (MG), methylene blue (MB), and crystal violet (CV) than pure Na2Ti3O7 and pure titanium peroxide, and the saturated adsorption capacities were 490.21, 386.13, 322.81, and 292.74 mg/g at 25°C, respectively. It was found that the pseudo-second-order kinetic model and the Langmuir model could well describe the adsorption kinetic and isotherm of cationic dyes studied. The results of this work are of great significance for environmental applications of TN-TP as a promising adsorbent material for dyeing water purification.
... The slightly enhanced corrosion rates and thicker films were attributed to the redox sensitivity of Ti and its ability to form Ti-H2O2 complexes (Tengvall et al. 1989a(Tengvall et al. , 1989b which are subsequently hydrolyzed leading to the high OH − content of the outer layers of the surface film. This has been more extensively demonstrated in more alkaline solutions (pH≥10) in which the formation of metastable complexes (Ti(OH)2O2) have been shown to form (Been and Tromans 2000;Rämo et al. 2002). ...
Zirconium alloys are widely used in nuclear reactors as fuel cladding and as reactor structural elements (i.e., CANDU reactor pressure tubes), and are therefore a component of the waste materials that could be emplaced in a deep geologic repository. Therefore, the corrosion mechanisms and rates for relevant zirconium alloys under repository conditions have been reviewed. Since titanium and zirconium alloys have many similarities, and because the data base for the corrosion of titanium alloys under repository conditions is considerably more extensive than that for zirconium alloys, the electrochemical and corrosion behavior of both materials have been compared and evaluated. Although electrochemical studies suggest Zircaloy cladding could be susceptible to pitting, redox conditions within a failed waste container will remain reducing and unable to support pitting. This leaves passive corrosion as the only long-term corrosion mechanism. The available data indicates that the rate of passive corrosion will be very low. A rate of 20nm/year would be a reasonable upper limit but it is likely the rate will be less than 1nm/year.
... Breakdown of the passive film and the associated pitting behavior is related to reduction film oxygen content in the region below the film. Attempts have been made to study the oxide layer formation on Ti articles in alkaline solutions (Wilhelmsen and Hurlen, 1987;Been and Tromans, 2000). The incorporation of Cl 2 ions into the oxide film on Ti alloy is a partial step for the initiation of defect-repairing oxide films such as Al(OH) 2 Cl, Al(OH)Cl 2 and AlCl 3 . ...
Purpose
The aim of this paper is to investigate the effect of cathodic charging and corrosion behavior of Ti‐48Al‐2Cr‐2Nb alloy in hydrochloric acid solutions.
Design/methodology/approach
TiAl alloy specimens of thickness 0.5 mm were cathodically charged in 0.1 M HCl solution at room temperature. The prominent current densities selected for this investigation were 25 and 50 mA cm ⁻² for durations of 24‐120 h. The change in weight of the specimen after charging was measured by a microbalance with an accuracy of ±1 μ g.
Findings
The nature of the specimen surfaces was characterized by X‐ray diffraction (XRD), auger electron spectroscopy (AES) and scanning electron microscopy (SEM) equipped with energy dispersive X‐ray spectroscopy (EDS). XRD revealed the phase transformation from microcrystalline to nano‐crystalline, particularly after high charging times (120 h) and high current density (50 mA cm ⁻² ). AES and EDS further assessed the compositional fluctuations on both cathodically charged and potentiodynamically polarized specimens. Surface corrosion leading to the generation of microcracks throughout the surface region was observed by SEM. Cathodic charging and the polarization process were responsible for embrittlement and pitting. Decreases in both weight and Vickers hardness values with an increase in charging time revealed that surface erosion depended strongly upon charging density.
Originality/value
The results presented in this work shed light on the role of alloying elements the passive behavior and their implications on their stability in hydrochloric acid environments.
... An indirect method to increase the overall (observed) capacitance of the anodically produced titania layers, is chemical etching with hydrogen peroxide in strong alkaline media [22], with an inorganic base or acid, or with "sealing" in boiling water [23]. Even though the capacitance of the electrodes was increased upon the successive immersions of the Ti/TiO 2 electrodes in the etching solution, the increase of the measuring capacitance is not solely attributable to the reduction of the thickness of the oxide layer. ...
The advantages and limitations of impedimetric sensors based on Ti/TiO2 architectures are described. Titanium dioxide (titania) was potentiostatically formed onto titanium electrodes of 2 mm diameter, at 10 and 30 V in 1 M H2SO4. The thickness of the titania layers was ellipsometrically determined to be 30 and 86 nm respectively and they are highly insulating with charge-transfer resistances in the MΩ range, as they were measured with electrochemical impedance spectroscopy under specific experimental conditions. Low voltage anodization (<10 V) results to amorphous TiO2, whereas at higher applied voltages (>25 V), anatase is the predominant form. SEM images are indicative of quite smooth, compact coatings without any severe cracks.
The disposal of scrap rubber, represented by retired tires, has achieved industrial achievements, but the handling of brass-coated steel wire as a structural reinforcement in retired tires has received little attention. A feasible and efficient method of acquiring economical resources is proposed to extract copper and zinc (Cu-Zn) from brass-coated steel wire. With 20% ammonia, 10% hydrogen peroxide, and a liquid-solid ratio of 10, the brass coating almost completely dissolved in 5 minutes. This technique may remedy the challenge of weak dissolving efficiency brought on by the dual phase microstructure of brass. Electrochemical measurements and density functional theory (DFT) simulations assist in verifying that hydrogen peroxide decreases the resistance of the corrosion and that OH- and O-2 in solution are the main contributors to the dissolution. In addition, the AH effectively enhances the corrosion of the α phase in brass, which is notably evident in comparable works. This effective strategy broadens the application of retired tires and provides a new method for extracting Cu-Zn resources.
Low-dimensional titanate nanostructures are gaining attention as a promising material for various photocatalytic applications. However, these conventional titanium oxide-based materials cannot utilize visible light because of their wide bandgap, and their synthesis generally requires high-alkali (10 mol L-1) and high-temperature (160-200 °C) conditions. Here, we report facile bottom-up synthesis for the visible light-activated peroxo-titanate nanoribbon (PTNR). The use of the peroxo-titanium complex ion containing the potassium ion as a precursor can induce the formation of a layered potassium titanate structure (K2-x H x Ti2O5) based on the self-organization reaction between titanium complex ions and potassium ions under mild synthetic conditions (0.29-4.39 mol L-1 KOH, 100 °C). Furthermore, the requirement of potassium ions in the formation of layered potassium titanate was stoichiometrically examined. The layered titanate crystals could be grown anisotropically, which depended on the radius of the cation used. Our results newly revealed that the larger radius of the interlayer cation promotes anisotropic crystal growth. As a result, in the case of the potassium base, a nanoribbon structure with a higher aspect ratio and larger specific surface area than those of lithium and sodium bases was formed. The formed peroxo-titanium functional groups significantly reduced the bandgap of titanate to 2.64 eV. In a photocatalytic decolorization test, the PTNR showed excellent photocatalytic performance based on the large surface area and enhanced light absorption in the visible light range while still performing well under UV light. These findings show not only that the proposed synthetic process has a low environmental impact but also that it contributes to the development of highly functionalized materials for photochemical applications.
This paper is devoted to study the electrochemical behaviour of the 316L stainless steel in hypochlorite sodium bleaching process. Experimental investigations can provide the following:-in the corrosion neighbourhood, standard electrochemical and impedance measurements evidenced a mass transfer, charge transfer process limitations at the electrode-The hypothetic pitting corrosion phenomenon is the consequence of the presence of Cl-ions which is induced by the pH solution.-The presence on Auger spectra of a chloride peak, provides that breaking of passive film is very sensitive to chloride ions-The surface Auger spectral analysis initiates the idea of the presence of a thin film, this hypothesis in reinforced by the electrochemical impedance measurements
Metallic biomaterials have been used enormously in biomedical devices and components, such as hard tissue replacements, cardiac and cardiovascular stents, etc., due to their desirable mechanical properties and biocompatibility. To improve the biological properties to meet the clinical requirements, chemical surface modification is often performed on the metallic biomaterials. This chapter reviews the various chemical surface modification methods of metallic biomaterials, including hydrogen peroxide treatment, acid treatment, alkali treatment, and thermal oxidation from the viewpoint of biomedical engineering. The appropriate chemical surface treatment can effectively expand the use of metallic biomaterials in the biomedical fields. Some of the recent applications are also discussed in this chapter.
The peroxo ligand is one of the most promising structure-directing agents in TiO2 nanocatalyst synthesis; however, its role in nanocatalyst growth and polymorph control is not well understood. Using a combination of scanning tunneling microscopy, X-ray photoemission spectroscopy, and kinetic Monte Carlo simulation, we show that the base-catalyzed reaction of H2O2 targets very particular sites on the rutile (110) surface, sites that are present in concentrations of less than 1% of a monolayer, producing highly homogeneous surfaces characterized by flat terraces and straight atomic-height steps. This reaction produces surface steps with a different orientation, different structure, and different reactivity from those prepared in ultrahigh vacuum studies. The observed reactivity is explained by a simple, site-specific model that is based on metal oxo coordination chemistry. This study shows that one of the principle roles of peroxide in etching and growth reactions is destabilizing neighboring bonds and increasing their lability. As a result, the peroxo ligand adds a degree of reversibility to growth reactions, thereby promoting the formation of well ordered crystals.
The photo-conversion efficiency and stability of back-illuminated dye sensitised solar cells with titanium foil based photoanodes are enhanced by a simple nitric acid treatment through which the foil is passivated. This treatment changes the morphology of the titanium foil and increases its electrochemical double layer capacitance.
Pollution control measures have resulted in replacement of chlorine by peroxide as
bleaching chemical. Change of chemical affects corrosion aspects, the suitability of
existing plant metallurgy and materials of construction of bleach plants. Accordingly
long term immersion and electrochemical corrosion tests were conducted on stainless
steel 304L, 316L, 2205 and 6% Mo and mild steel in peroxide solutions of pH 10. The
materials were tested for uniform corrosion, pitting and crevice corrosion and attack
around the weld area. Corrosion attack estimated from long term immersion tests is
found in agreement, by and large, with that analyzed from electrochemical test. E-pH
diagrams drawn for water-peroxide system have been used to understand the corrosivity
of the peroxide media. An attempt has been made to suggest a suitable material of
construction for handling the test media on the basis of degree of corrosion attack on
them and their cost and the mechanical properties.
To improve the bioactivity and antibacterial properties of biomedical titanium implants, many efforts have been made to modify its surface composition and topography. In this work, biomimetic hierarchical micro/nanostructured titania films were formed on titanium surfaces via acid etching to generate microtopography and subsequent hydrothermal treatment to produce titania nanopetals or nanorod layers on it. In view of the potential clinical applications, the apatite-forming ability of the hierarchical micro/nano-textured TiO2 films was evaluated by simulated body fluid (SBF) immersion tests, and Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used to estimate the bacteriostatic effect. Meanwhile, the osteoblast-like cell line MG63 was cultured on the surface of the films to investigate their cytocompatibility. Compared to the microtopography, the hierarchical micro/nano-textured surfaces exhibit better apatite-forming ability and bacteriostatic effect on S. aureus, as well as enhancing the proliferation of MG63. The results obtained in this work suggest that the hierarchical micro/nano-textured TiO2 films on titanium may be a potential candidate for bone tissue engineering and biomedical implants. Our study reveals a synergistic effect on bioactivity and bacteriostasis as well as cell responses exerted by the titania nanofilms with biomimetic micro/nanotopographies and provides insight into the design of better biomedical implant surfaces.
The corrosion behavior of titanium in hydrogen peroxide solutions was studied by measuring the titanium ions concentration using spectrophotometer. The influence of additives (K+, Ca2+, Na+, Mg2+, Cl-, HPO42-, H 2PO4-) on the corrosion behavior of titanium was examined. The results indicated that Ca2+ exhibited the highest inhibition to the titanium corrosion in hydrogen peroxide solutions, while HPO42+ behaved as an accelerator to the corrosion. It was suggested that the Ca2+ was absorbed on the titanium surface to form a thin film of CaTiO3 or CaO2, and consequently, inhibited the corrosion of titanium. The acceleration of the titanium corrosion in the present of HPO42- was caused probably by the increased defect of surface oxide films after absorption of HPO42- ions.
Uniform corrosion of titanium was studied in alkaline hydrogen peroxide environments simulating pulp bleaching conditions. Corrosion rates of unalloyed Grade 2 and alloyed Grade 5 were determined as a function of hydrogen peroxide anion (HOO−) concentration. Influences of calcium and silicate inhibitors and iron and manganese were investigated. Without inhibition titanium corroded at HOO− content of 200 mg/l: Grade 2 0.4 mm/y and Grade 5 1.4 mm/y. Addition of calcium (Ca2+) and silicate (SiO32−) diminished the corrosion of Grade 2 to critical anion level 400 mg/l, but could not protect Grade 5 even at the HOO− concentration of 300 mg/l. Presence of iron and manganese raised the critical levels of the both grades. High HOO− anion level was observed as a notable potential difference between titanium and platinum.
Gleichmäßige Flächenkorrosion von Titan unter alkalischen Wasserstoffperoxidbedingungen: Einfluss der Übergangsmetalle und der Inhibitoren Kalzium und Silikat
Gleichmäßige Flächenkorrosion von Titan wurde in alkalischen Wasserstoffperoxidbedingungen, die Papierbleichbedingungen simulieren, untersucht. Die Korrosionsgeschwindigkeiten von unlegierter Güteklasse 2 und legierter Güteklasse 5 wurden als Funktion der Wasserstoffperoxidanionen(HOO−)konzentration bestimmt. Einflüsse von Kalzium- und Silikatinhibitoren sowie von Eisen und Mangan wurden untersucht. Ohne Inhibierung betrug die Korrosion von Titan bei einem HOO−-Gehalt von 200 mg/l bei der Güteklasse 2 0,4 mm/Jahr und bei der Güteklasse 5 1,4 mm Jahr. Die Zugabe von Kalzium (Ca2+) und Silikat (SiO32−) verminderte die Korrosion der Güteklasse 2 auf ein kritisches Anionenniveau von 400 mg/l; konnte aber Güteklasse 5 selbst bei einer HOO−-Konzentration von 300 mg/l nicht schützen. Die Anwesenheit von Eisen und Mangan erhöhte die kritischen Niveaus für beide Güteklassen. Hohe HOO−-Anionengehalte wurden als beträchtliche Potentialdifferenz zwischen Titan und Platin beobachtet.
The effect of ultrasonic treatment under conditions of acoustic cavitation on the pickling and brightening of titanium and its alloys in acidic solutions containing various oxidants and in alkaline solutions is studied. It is shown that the liquid cavitation close to the metal surface pickled intensifies the pickling and brightening processes several times. The reasons for the effect are discussed. Intense acoustic cavitation can make water molecule split and produce free radicals and hydrogen peroxide. When collapsing, cavity bubbles eliminate capillary limitations and intensify the access for pickling solution to the oxidized metal surface. While pulsating, they promote degassing the solution and removing hydrogen bubbles from oxidized metal surface, thus freeing the access for solution. The cavitating ultrasonic intensification of industrial surface treatment of titanium and its alloys is recommended.
Hydrofluoric acid offers a fast etching rate for removing 200 μm-thick alpha-cases from the surfaces of cast Ti-6Al-4V. The acid picks up hydrogen gas into substrate of the cast, which can be limited by introducing an oxidizing acid. This study proposes the optimal ratios of hydrofluoric/nitric acid as the pickling solutions. The cast Ti-6Al-4V in these solutions is monitored with chemical etching and electrochemical polarization. The mechanisms of etching procedures are initiated by generating oxygen vacancies that lead to several products from a series of quasi-chemical steps. The final product of the reactions may deduce as the form of H2TiF6 that is peeled out by the evolution of produced gases. Polarized curves are performed to illustrate passive behaviors of the alpha-case removed Ti-6Al-4V. The amounts of charge transference increase with increasing hydrofluoric acid concentrations. The newly formed passive film was estimated to be 20 nm in thickness with non-stoichiometric arrangements in the 4% HF electrolyte.
Zugl.: Hannover, Universiẗat, Diss., 2003.
Grade 12 titanium is a possible canister material for the storage of high-level nuclear wastes. Changes in the oxide responsible for decreased hydrogen absorption under gamma radiation are caused by the radiolysis products of the brine solution. gamma radiation also increases the pitting potential in 1 M KBr solution at 25 C. Among the radiolytic products, hydrogen peroxide plays an important role in determining the corrosion conditions in the irradiated brine solution.
A general treatment has been developed which describes the entropies of ions in solution in terms of various ionic and solvent parameters. By using the entropies themselves at some reference temperature to define these parameters, it is possible to derive a principle of entropy correspondence for ions between different temperatures. If the standard state is chosen properly by fixing the entropy of H+(aq) at each temperature, then the ionic entropies at one temperature are linearly related to their corresponding entropies at 25°. A generalized treatment of nonaqueous solvents also follows directly from the theory. Various equilibria and thermochemical data from the literature have been used to calculate the partial molal entropies for over forty solutes, and a consistent set of ionic entropies is given for higher temperatures. These experimental entropies are in good agreement with the correspondence principle, and preliminary constants are given to allow the prediction of entropies up to 200° for the common types of ions.
Equations are given for calculating heat capacities at 25° and at elevated temperatures from the correspondence principle for entropies previously developed.
The anodic oxide film on titanium has been studied by ellipsometry and SEM observation. Ex situ multiple‐angle‐of‐incidence and in situ ellipsometric measurements allow the complex refractive index to be estimated at for the titanium substrate and at for the anodic oxide film at wavelength 546.1 nm. The anodic oxide film thickness increases linearly with potential in a range from −0.55 to 7.5V (RHE) at the rate of 2.8 nm V⁻¹ in phosphate solutions of pH 1.6–12.1, 2.5 nm V⁻¹ in solution, and 2.4 nm V⁻¹ in solution. At potentials more positive than 7.5V, the film breaks down, leading to the formation of a thick oxide film probably due to an increased ionic current through the breakdown sites. The film composition is estimated to be or , which suggests the presence of hydroxyl bridge in its bonding structure.
The passive behaviour of titanium in alkaline acetate, borate and carbonate solutions of pH 7–13 has been studied by quasi-stationary (20 h stabilization) and transient polarization measurements and by dc capacitance determinations over potentials from −0.75 to 2.5 V(sce), all at 25°C. Titanium exhibits approach to active/passive transition at low potentials, regular passive behaviour with nearly pH independent passive current over an intermediate potential range, and electron extraction from solution species at higher potentials. In the regular passive region, potentiostatic transients accord with the Cabrera—Mott equation. Capacitance data largely obey expectations from an “insulator” model, revealing the main charge distribution at the passive titanium electrode. They also combine with previous ellipsometric data to give values around 60 for the static dielectric constant of the passivating oxide film.
Processes of anodic passivation and corrosion behaviour of titanium and binary titanium alloys in non-oxidising acids at elevated temperatures have been investigated, when the alloy dissolution in the passive state proceeds at certain rate.The main control of dissolution in the passive state is determined not by chemical stability of a passive film (in most alloys it turns out to be of the same order as in pure titanium) but by the value of its ionic (cationic) conductivity.For highly-alloyed (Mo, Cr, Ta) hardened titanium alloys having a single-phase structure it has been established that their transition to the passive state is facilitated (smaller passivation currents) in comparison with the same alloys in annealed state having a two-phase structure. At the corrosion of two-phase alloys the surface is enriched with the more stable phase. For Ti-15Mo alloy in the active region of potentials, the β-phase is accumulated on the surface, α-phase is mainly dissolved. On the contrary, at transpassivation the β-phase (containing greater amounts of Mo) is chiefly dissolved. For two-phase Ti-15Cr alloy in transpassivation region, the γ-phase, enriched with chromium, is principally dissolved.
The electrochemical oxidation of Ti electrodes in
,
, and
electrolytes has been followed by in situRaman spectroscopy. The transformation of amorphous Ti‐oxide films to the anatase, brookite, and rutile mineral forms is described
in terms of the nature and concentration of the electrolyte, the applied anodizing voltage and current, and the anodization
time. Under certain conditions, the crystallization of anatase is found to occur from a film of amorphous Ti‐oxide without
any changes in film thickness. Crystallization occurs after the film breakdown. Evidence for the formation of brookite has
been obtained after controlled oxidation of a Ti electrode in
electrolyte.
Ellipsometry and antibody techniques were used to investigate plasma protein adsorption onto titanium (Ti) surfaces pretreated in hydrogen peroxide (H2O2). Surfaces preincubated for short times in 10 mm or 100 mm H2O2 bound relatively large amounts of anti-high molecular weight kininogen (a-HMWK) after immersion in blood plasma. Increasing the preincubation time in H2O2 led to an increase in the total amount of bound plasma proteins and a large deposition of anti-fibrinogen (a-Fib). Large amounts of a-HMWK and a-Fib were also deposited onto surfaces washed in trichloroethane, acetone and ethanol, whereas radiofrequency plasma-treated surfaces or surfaces incubated in deionized water bound preferentially a-HMWK after plasma immersion.Auger electron spectroscopy (AES) made on Ti-surfaces preincubated in 10 mm and 100 mm H2O2 solutions showed an increased oxide thickness and, after 16 h of immersion in a physiological buffer, an increased amount of calcium on and throughout the oxide. The rate of net oxide growth was larger in 10 mm than in 100 mm H2O2
A stable titanium-peroxy-radical complex is formed when metallic titanium interacts with hydrogen peroxide. The radical appears as one component in an aqueous gel formed when excess peroxides have been (catalytically) decomposed. The interaction between titanium and hydrogen peroxide may be of importance also in vivo during an inflammatory response at the implant. We report in this paper on the bactericidal effects of the titanium gel in the lacto- and myeloperoxidase-halogen systems. Escherichia coli viable count was used to evaluate the bactericidal properties of the gel and of H2O2 for comparison. The gel had only small or no toxic properties at high dilutions. Higher concentrations of the gel had bactericidal properties similar to those of H2O2. The results indicate that at physiological pH, the decomposition products of the gel ae titanium hydroxide (Ti(IV)(OH-)4) and hydrogen peroxide (H2O2). It was found that the gel probably oxidizes glutathione directly in contrast to H2O2, which needs a peroxidase to do so. A model for the interaction between titanium and hydrogen peroxide is suggested. Its consequences for the properties of titanium in vivo are also discussed.
Electrochemical measurements, x-ray photoelectron spectroscopy, and scanning tunneling microscopy have been used to study the effect of hydrogen peroxide on the passivity of titanium in a phosphate-buffered saline (PBS) solution. The results indicate that the passive film formed in the PBS solution--with and without addition of H2O2--may be described with a two-layer structure model. The inner layer has a structure close to TiO2 whereas the outer layer consists of hydroxylated compounds. The introduction of H2O2 in the PBS solution broadens the hydroxylate-rich region, probably due to the formation of a Ti(IV)-H2O2 complex. Furthermore, the presence of H2O2 results in enhanced dissolution of titanium and a rougher surface on a microscopic scale. Finally, a dark pigmentation (blue color) is observed when titanium has been exposed--for several weeks--to PBS with additions of H2O2.