FIGURE 9 - uploaded by Jing Liu
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The experimental flow diagram of oxidation and surface relaxation experiments and the corresponding schematic of titanium oxide films: (a) oxide films formed in the absence of Cu 2+ ; (b) oxide films after adding Cu 2+ ; (c) Cu 2+ in the oxide films was reduced to Cu 0 during the relaxation process; (d) Cu 0 was oxidized to Cu 2+ during the reapplied process.
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Titanium is chosen as the construction material of autoclaves for pressure acid leaching of metal ores. The corrosion behavior of titanium was studied in sulfuric acid solutions with different additions of Cl−, Cu2+, and Fe3+ to simulate hydrometallurgical lixiviants at 25, 55, and 85°C. Electrochemical methods like open-circuit potential measureme...
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... following sequence was adopted and the ex- perimental fl ow diagram is shown in Figure 9. In the beginning, PS experiments were performed to form a copper-free titanium oxide fi lm before introducing Cu 2+ Using the above procedure, oxidation and sur- face relaxation experiments were conducted with the desired potential of 1.0 V at 85°C. ...
Citations
... During the service of the SEC pipes, the addition of the cupric fungicide to prevent microbial corrosion, the corrosion of copper components, or other reasons could lead to the local enrichment of Cu 2+ in the SEC system and the precipitation of Cu on the surface of components; the interaction between Cu 2+ and seawater may accelerate the corrosion of SEC system material, even leading to the breaking of the components and inducing the addition of Cu 2+ into the secondary circuit system. Presently, the corrosion of steels in seawater had been widely investigated all over the world [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], and the influence of Cu 2+ on material corrosion is mainly focused on different materials in nonseawater environment, such as steel [21][22][23][24][25][26][27][28][29][30], aluminum alloy [31,32], 690 alloy [33], and copper alloy [34]. However, the works focused on the corrosion behavior of steels in seawater containing Cu 2+ and the influence of the Cu 2+ and copper oxides on the corrosion of the equipment in the secondary circuit system were little reported [35]. ...
The corrosion behaviors of A106B carbon steel and 304L stainless steel (SS) in seawater with different Cu²⁺ concentrations were studied by the immersion test and the potentiodynamic polarization test. The results showed that with the increasing Cu²⁺ concentration, the mass lot rates of A106B and 304L SS all increased in the immersion test, and compared with A106B, the mass lot rates of 304L SS were all smaller. In the potentiodynamic polarization test, following the concentration of Cu²⁺ increased, the corrosion potential of A106B firstly shifted negatively; then, when Cu²⁺ increased to 100 ppm, the polarization curve moved to the upper right direction; namely, both the corrosion potential and corrosion electrical density increased. The corrosion potential of 304L SS increased with the increasing Cu²⁺, and the passive region was reduced; the pitting sensitivity improved.
... They are widely used in the hydrometallurgical industry because they provide outstanding corrosion resistance in various oxidizing acidic environments, even in the presence of halogens and some reducing acid electrolytes like sulfuric acid [2]. They can be used, for example, as autoclave internals in the high-pressure acid leaching of nickel laterites or in the pressure oxidation of refractory gold ores and concentrates, or within heat exchanger apparatae [3][4][5][6]. ...
The corrosion, passive layer characteristics, and surface morphology of Ti-45Nb in fluoride-containing H2SO4 solutions are evaluated through electrochemical measurements and surface profilometry. Ti-45Nb spontaneously passivated in solutions with 0 and 0.0025 M F⁻, contrasting with the active-passive behaviour observed at 0.025 and 0.05 M F⁻. The corrosion resistance of Ti-45Nb decreases with increasing fluoride concentration: the passive current density in 0.05 M F⁻ is 207 µA/cm², which is eight times greater than the value obtained in 0 M F⁻ (26 µA/cm²).
... Erosion-corrosion attack of these autoclave parts is a safety concern. The leaching conditions are usually very aggressive, involving concentrated sulfuric acid (H 2 SO 4 ) or a mixed sulphate-chloride system under high temperature high pressure conditions [12][13][14]. Titanium and its alloys are widely used for the liner and internal parts of autoclaves. Unalloyed titanium, such as ASTM grades 1 and 2 (Ti-1, Ti-2), is used as an internal autoclave shell liner and as internal chamber walls (known as weirs). ...
... Grade 7 (Ti-7, 0.15% Pd alloyed) is usually employed to repair any corrosion damage-it has superior resistance to crevice corrosion [15,16]. The corrosion behaviour of titanium has been extensively investigated and its high corrosion resistance is widely acknowledged in stagnant simulated leaching solutions [14,[16][17][18]. Its corrosion resistance is attributed to the extremely inert passive oxide film that spontaneously forms on its surface. ...
... So far, the test solutions, such as the acid solutions or brine solutions [5,8,10,19,[21][22][23], under which most of the available titanium erosion-corrosion data were obtained, are quite different from hydrometallurgical leaching solutions. Hydrometallurgical solutions are typically highly acidic, and involve a large amount of oxidative species, such as oxygen, ferric and cupric ions [14,28]. The effect of temperature, which is an important consideration for corrosion processes, is barely addressed in the previous work [19,29]. ...
Electrochemical techniques were used to investigate the erosion-corrosion of titanium in simulated acidic mineral leaching slurries. Erosion-corrosion of titanium was caused by solid particle impingement. Electrochemical noise revealed that solid particle impacts resulted in localised fracture of the passive film, and erosion-corrosion of titanium proceeded in the form of current transients. As conditions become more abrasive, erosion-corrosion is an increasing threat to titanium equipment exposed to acidic slurries.
... A stable oxide layer (by heating the interlayer with Sb and Sn elements) could be created on the Ti substrate as the greater amount of more oxidized species (Sb and O) and higher binding energies of Sb and Sn were observed (Fig. 3c-f and Table S2). The oxide layer on the Ti substrate can act as a protective layer against oxidation/corrosion of the Ti base material [45,46] and thus, yield the greater durability of the Ti/TiONC/Sb-SnO 2 electrode (compared to the control electrode). ...
Ti-based Sb-SnO2 electrodes are attractive due to their excellent catalytic activity but have a short service life. Here, we report a highly stable and efficient Ti/TiONC/Sb-SnO2 electrode, which was fabricated through hydrothermal reactions using urea to form TiONC interlayers and electrodeposition-annealing to coat the active Sb-SnO2 catalysts. The triple-layered anode was characterized by highly crystalline structures, high oxygen evolution potentials, and corrosion-resistance properties. The structural arrangement yielded better electrocatalytic performances than that using the control electrode (Ti/Sb-SnO2), showing enhanced organics degradation efficiencies. This new electrode's lifetime was significantly (~25 times) longer than that of either the control or any Sb-SnO2 electrode modified with non-precious materials reported in the literature. The electrode's enhanced stability was attributed to the insertion of the mixed C and N interlayers that are resistant to oxidants and corrosive ions. The Ti/TiONC/Sb-SnO2 anode holds promise for use in electrochemical water treatment.
... The application fields requiring titanium for its corrosion resistance range from offshore plants, acid environment, aerospace, 6,7 automotive, high temperature, chemical and food industry, [8][9][10] marine hydrometallurgical application and even nuclear fuel wastes containment. 1,[11][12][13][14] In such aggressive environments, even titanium may suffer different forms of corrosion. 15,16 The most critical of them are due to the localized breaking of the passive layer, favored by the presence of concentrated halides, such as hot salty water (above 200°C) or bromide containing species. ...
Anodization is an easy and reliable treatment to improve titanium corrosion resistance in severe environments. In previous studies, its effectiveness in enhancing oxide film resistance in halides was correlated with anodization cell voltage. To increase treatment industrial applicability, energy efficiency has to be maximized. For this purpose, a gravimetric approach was applied to study oxygen evolution during titanium anodic oxidation. Anodization efficiencies, calculated from real time O2 evolution measurements, were used to determine the most efficient galvanostatic anodization treatment by comparing different anodic current densities, from 1 to 20 mA cm⁻², and different electrolytes (H2SO4−K2SO4). Anodization cell voltages were correlated with oxide thickness through indirect spectrophotometric measurements to compare the amount of charge needed to reach a certain film thickness in different anodization conditions.
... This resistance is due to a thin (1.5 nm-10 nm) [3] but compact oxide layer that is naturally formed when the metal is exposed to the air. For this property, together with high strength, high fracture toughness and low density [4,5], titanium is used where other metals would fail, such as offshore, acid environment, aerospace [6,7], automotive, high temperature, chemical & food industry [8][9][10][11][12][13][14]. ...
Anodized titanium shows an excellent resistance to pitting corrosion. However, it could be subject to failure in case of local removal of the oxide film due, for example, to incorrect handling during transport, installation, or use. Depending on part size and usage, an electrochemical anodizing treatment could be not feasible. In this case, localized chemical oxidation treatment could be used to recover damaged film and restore corrosion resistance. Chemical oxidation was performed on titanium by immersion in NaOH 10 M and H 2 O 2 10 M at temperature from room to 90 °C with duration ranging between 1 h and 72 h. Potentiodynamic tests in bromides 0.5 M were used to determine the effectiveness of the treatment in relation with the one obtained with anodic oxidation. Higher bath temperature led to faster growth of the film, however it has no effect on the final corrosion resistance. Breakdown potential in bromides increased with treatment duration. The establishment of a plateau occurs at earlier stage, as temperature is increased. Titanium samples anodized and then scratched, to simulate film mechanical removal, were recovered using chemical oxidation and initial corrosion resistance was restored. The suggested treatments for in-situ recovery are 72 h of exposure to NaOH or 6 h at H 2 O 2 at room temperature.
... However, the addition of Cu(II) generally resulted in lower R p values than Fe(III) once passivation had been attained when the temperature was higher than 30 • C, indicating a slightly lower corrosion resistance of titanium for this condition. A similar phenomenon was also reported by Liu et al., 15 where the modest addition of Fe(III) (1.0 g/L) enhanced the corrosion resistance of titanium more significantly than Cu(II) (15 g/L). The higher corrosion resistance of Ti-2 achieved by Fe(III) than that of Cu(II) was further verified in the following sections. ...
The passivation of Ti-2 by Fe(III) and Cu(II) species in acidic chloride solutions was investigated by electrochemical techniques. It was found that the critical concentrations of Fe (III) and Cu(II) species required to induce passivation of Ti-2 increased from 1.0 ± 0 to 6.0 ± 0 mM and from 0.25 ± 0 to 1.15 ± 0.23 mM, respectively, when the temperature was increased from 30°C to 80°C. The mechanism associated with the passivation was the acceleration of the cathodic reactions due to the introduction of oxidants for Ti-2. Cu(II) was more effective than Fe(III) at inducing the passivation of Ti-2 for the conditions investigated here.
... For this property, together with high strength, high fracture toughness and low density, [4,5] titanium is used where other metals would fail, such as offshore, acid environment, aerospace, [6,7] automotive, high temperature, chemical & food industry, [8][9][10] marine hydrometallurgical application, and nuclear fuel wastes containment. [11][12][13][14] In such aggressive environments, commercially pure titanium may suffer different form of corrosion. Generalized corrosion is caused by small quantity of fluorides ions (more than 0.002 M [15] ) that combining with titanium forms a soluble complex (TiF 4 ), destroying passivity film. ...
Titanium owes its astounding corrosion resistance to a thin, compact oxide layer that is formed spontaneously when the metal is exposed to the environment. However, even titanium can be subject to corrosion in very aggressive environments. To enhance its corrosion resistance, it is possible to exploit the same mechanism that leads to the formation of the protective oxide layer and force its growth with an external contribution. Oxidation can be easily stimulated with the use of an electrochemical cell. However, when part geometry or dimensions do not allow the immersion in an anodizing bath, chemical oxidation can be used. This study compares corrosion resistance enhancement after NaOH and H2O2 treatment. Treatment duration and temperature, solution concentration, and quantity are optimized to achieve the best corrosion resistance with the least time and chemicals consumption, by maintaining the process easy to perform and safe for the operator. This study compares corrosion resistance enhancement of titanium by chemical oxidation treatment with NaOH and H2O2. Treatment duration and temperature, solution concentration, and quantity are optimized to achieve the best corrosion resistance with the least time and chemicals consumption, by maintaining the process easy to perform and safe for the operator.
... The behaviour of Ti in aqueous acid solutions has, for decades, been studied by numerous authors, cf. [18][19][20][21][22][23][24][25]. The Ti behaviour is governed by the stability of the passive layer under the given conditions. ...
Proton exchange membrane water electrolysis (PEM WE) suffers from several issues, such as the high cost and low stability of the electrolyser unit components. This is especially evident for an anode polarised to a high potential and in contact with an acidic membrane. Such a combination is detrimental to the vast majority of electron-conducting materials. Nowadays Ti (possessing a protective passive layer on its surface) is used as the construction material of an anode gas diffusion layer. Since the passivation layer itself is non-/semiconducting, an excessive degree of passivation leads to high surface contact resistance and to energy losses during PEM WE operation. This problem is usually solved by coating the Ti surface with precious metals. This leads to a further increase of the already very high cell investment costs. In this work an alternative method based on appropriate Ti etching (in acid) is presented. The (surface) composition of the samples treated was investigated using SEM, X-ray fluorescence and diffraction and photoelectron spectroscopy. TiHx was found in the subsurface layer. This was responsible for preventing excessive passivation of the Ti metal. The superior performance of the etched Ti gas diffusion layer (compared to non-etched) in a PEM water electrolyser was confirmed during an (> 100 h) experiment with current densities of up to 1 A cm− 2. Using the described treatment the surface contact resistance was substantially reduced and its increase during PEM WE operation was largely suppressed. As this method is very simple and cheap, it has tremendous potential for improving PEM WE process efficiency.
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... Titanium has outstanding corrosion resistance due to a thin, amorphous, non-stoichiometric TiO 2 protective layer (max 10 nm thick [1] ) that is formed spontaneously on the surface when exposed to aerated environment. This protective layer is very stable and allows the use of titanium in severe working conditions, such as offshore, acid environment, aerospace, [2,3] automotive, high temperature applications, chemical and food industry, [4][5][6] marine hydrometallurgical application, and nuclear fuel wastes containment, [7][8][9][10] where no other metal can be used. ...
The corrosion behavior of commercially pure titanium (UNS R50400, ASTM grade 2) was investigated in presence of aggressive, bromides containing, species, reported to cause severe localized corrosion compared to chlorides. To enhance localized corrosion resistance of the metal, several surface treatments were performed. Samples anodized at potentials between 10 and 200 V were characterized in term of oxide thickness and morphology and tested with potentiodynamic analyses in ammonium bromide solution. Base metal was prepared both with etching and mechanical polishing pre‐treatment, to enlighten the effect of pre‐treatment sample preparation on post‐treatment corrosion resistance. To enhance titanium corrosion resistance in halide containing solution an anodizing treatment is proposed, consisting in applying an anodic voltage of several tens of volts to the metal, promoting the artificial growth of the titanium oxide. A wide range of anodizing voltages, up to 200 V, has been considered. Obtained results are promising; all the tested anodized samples enhanced corrosion resistance.
