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Abstract
The commercial importance of tungsten in industry is related to its traditional uses: incandescent light filaments, additions to steel to improve hardness, and its use as tungsten carbide; the last two applications are related to use in tools for metal working. However, tungsten has several niche applications in its own right and some interesting electrochemical properties, a number of which are considered in this article.
... Tungsten exhibits exceptional mechanical and corrosion properties [5,6]. Recently, increased interest has been shown in silver-tungsten alloys as connectors for electrical and electronic purposes. ...
The reduction of tungstate ions in aqueous solution is often referred as induced codeposition. Those ions can only be reduced to a metallic state alongside another element which is mostly nickel. However, other metal such as cobalt and iron are reported in the literature. Various hypothesis have been made concerning the precise mechanism behind induced codeposition, but even if the exact role of the various chemical species isn’t fully understood, tungsten was successfully electrodeposited using more noble element such as copper and silver [1].
Silver electroplating is a widely used process in the connector industry. In fact, while silver coatings exhibit an extremely high thermal and electrical conductivity, they remain highly vulnerable to sulphuration and present poor mechanical properties both in hardness and wear resistances. For these reasons, electrodeposition of silver alloys has aroused a recent interest, relying on an alloying element addition that would compensate silver weaknesses. Alloy compounds inducing high mechanical and chemical resistances such as tungsten, are obvious candidates.
Moreover, limitations in free cyanide use in electroplating processes is an active research subject. While gold-cyanide complexes are stable enough to be used without any cyanide ions in solution, silver complexation in alkaline baths is highly dependent on high free cyanide concentrations. Processes using thiosulfate, nitrogen heterocyclic compounds or methane sulfonate were proposed as replacement solutions, but they are still under investigations [2].
The present study is part of the SILAHPERF project, led by IRT-M2P and UTINAM Institute, which try to investigate the codeposition mechanism of various silver-based alloys of interest with a particular focus on silver-tungsten while seeking for environmental-friendly solutions. A cyanide-free silver-tungsten plating bath is proposed and resulting coatings are characterized by various techniques (SEM, XRD, GDOES...). Resolutely intended for connector applications, functional properties such as hardness, wear resistance and electrical conductivity of the deposit were evaluated depending on bath composition and electrolysis parameters.
[1] A. Kola, X. Geng, and E. J. Podlaha, ‘Ag–W electrodeposits with high W content from thiourea–citrate electrolytes’, Journal of Electroanalytical Chemistry , vol. 761, pp. 125–130, Jan. 2016
[2] B. Satpathy, S. Jena, S. Das, and K. Das, ‘A comprehensive review of various non-cyanide electroplating baths for the production of silver and gold coatings’, International Materials Reviews , vol. 68, no. 7, pp. 825–861, Oct. 2023
... Tungsten exhibits exceptional mechanical and corrosion properties [5,6]. Recently, increased interest has been shown in silver-tungsten alloys as connectors for electrical and electronic purposes. ...
Silver-tungsten coatings were successfully electrodeposited on platinum and copper substrates from a non-toxic 5.5-dimethylhydantoin electrolyte at low pH and two different carboxylic acid forms: citrate or tartrate. Tungsten contents remain at low levels compared to former works, but close to the values considered as optimal for functional properties without having to recourse to controversial substances such as thiourea. Electrochemical studies by linear sweep voltammetry allow to distinguish two typical behaviors and give interesting insight into the induced codeposition mechanism. Silver-tungsten codeposition only occurred at pH 2.0 and 3.5 using citrates and at pH 2.0 using tartrates, corresponding to the forms H3Cit, H2Cit-, and H2Tar, respectively. No silver-tungsten reduction was possible with less than two protonated carboxyl groups on either tartrate or citrate ions. Separate silver and tungsten lattice are both present in the resulting alloy. Grain and crystallite sizes were observed by SEM. XPS investigations show that for our low W content alloys, silver is found to be metallic whereas tungsten is present in oxide form. The carbon peaks and also gaps between peaks when N is absent indicate that citrates are present in the coating, unlike DMH.
... From the Pourbaix diagram, a protective layer formation is expected to protect the tungsten surface up to pH = 5. At higher pH values, the protective layer (likely WO 3 ) will form tungstic ions (Equation (1)) [15,16]. ...
Tungsten has unique physical and chemical properties that make it ideal for high-temperature applications. At room temperature, it is being considered for medical applications due to its protection by an oxide/hydroxide film. However, breakdown of the oxide film and tungsten dissolution can have adverse effects on human health. This study investigates the corrosion of tungsten with and without dispersed oxides of rare-earth elements (ThO2, CeO2, and La2O3) in a 3 wt-% NaCl solution using electrochemical techniques. The results suggest that tungsten dissolution occurs after the formation of an oxide film, likely WO3, on the surface of tungsten and dispersed oxide tungsten. La2O3 and CeO2 may decrease the corrosion rate of tungsten, while WThO2/tungsten has similar corrosion rates to tungsten. The study concludes that CeO2 or La2O3 could replace ThO2 in tungsten due to the radioactive nature of Th.
... Tungsten forms many relatively insoluble complexes with chloride ions, and its protecting factor is a result of its probable reaction with chloride, which fills the pores with a film of corrosion products. Tungsten has domains of passivity associated with WO2 and WO3 with the latter material having low solubility and being stable to further oxidation [34]. These protective films, constituted mainly by metal oxide/hydroxides, separate the coating surface from electrolyte and raise the impedance modulus of the coating during immersion time [31]. ...
Hard nanocrystalline Ni-Co or Ni-W coatings are receiving a growing interest owing to their premium hardness, wear, and corrosion properties for several industrial applications. Furthermore, surface hydrophobicity greatly improves surface corrosion resistance. In this research, the durability of hydrophobic hierarchical NiW electrodeposited film has been evaluated in a high-speed slurry erosion–corrosion (EC) test rig. Two different coatings have been tested: a rough coating obtained in a chloride-based bath (NiWchloride) and a smooth coating obtained in a sulfate-based bath (NiWsulfate). Corrosion behavior over time was evaluated by electrochemical impedance spectroscopy (EIS), while surface hydrophobic performance was determined by the sessile drop method. The morphological features of the coatings were assessed by scanning electron microscopy while roughness modification during the EC tests were identified by means of an atomic force microscopy. During static immersion in the aggressive solution, the impedance modulus of the coatings continuously increased due to an increase in the thickness of corrosion products. During the EC test, the impedance modulus of the smooth NiW coating decreased, losing its barrier property. It was observed that the increase in impedance modulus of the hierarchical structure of the rough NiW coating during EC was far greater than that during static immersion. After 64 min of EC, the NiWchloride was able to resume its hydrophobicity property by storing in air; nevertheless, the NiWsulfate, with a loss of approximately 72% in its initial contact angle, was no longer hydrophobic. The results showed improvements in the lifetime of hydrophobic NiW coatings in erosion–corrosion conditions of the hierarchical nanostructure obtained in a chloride-based electroplating bath.
By referring to the fact that corrosion rates alter upon variation of different conditions and no research relevant to Lebanon address corrosion issues yet, this study was conducted based on accurate Lebanese offshore data and water composition. Based on "Alloy Select Software", identifying the most suitable material from different alloys was revealed, which turned out to be Copper and Aluminum based alloys. Moreover, corrosion rates were detected under different conditions of Temperature, CO₂, and H₂S and then repeated in the presence of a corrosion inhibitor. Results of these studies proved the significant influence of high temperature accompanied with high CO₂ percentage. However, different results concerning low temperature with different percentages of H₂S were obtained.
https://rdcu.be/cd0vl
Thermally sprayed cermet coatings are adequate solutions to improve cavitation and wear resistance of hydraulic turbines made of stainless steel (SS), especially in rivers with a high sediment load, such as the Madeira River in Brazil. However, some cermets are easily dissolved in river water, leading to premature failure of the coating and costly maintenance. Moreover, galvanic corrosion induced by coupling the cermet to a SS can accelerate the coating dissolution. Therefore, the corrosion resistance of six cermets (WC-12Co, WC-10Ni, WC-10Co-4Cr, Cr3C2-25NiCr, Cr3C2-10NiCr and Cr3C2-10Ni) and the galvanic corrosion resistance of these materials coupled to CA6NM SS were evaluated in a solution that simulated Madeira River water. WC-12Co and WC-10Ni cermets exhibited the highest corrosion rates, 0.077 and 0.068 mm/year, respectively, whereas the Cr content in the WC-10Co-4Cr (0.017 mm/year) and Cr3C2-based coatings (0.005 to 0.007 mm/year) led them to corrode at slower rates. Moreover, the WC-10Co-4Cr and Cr3C2-based cermets exhibited negligible galvanic corrosion current when coupled to the CA6NM SS, making them good options to coat hydraulic turbines. In contrast, WC-12Co and WC-10Ni coatings underwent a more severe galvanic corrosion process, which would drastically reduce the lifespan of these materials as hydraulic turbine coatings.
The corrosion behavior of W-Cu alloys, pure Cu and W at different pH was investigated using electrochemical measurements and immersion test. The corrosion behavior and the preferentially attacked phase of the W-Cu alloys changed with pH values as micro-galvanic effect between Cu binder and W phase played a significant role. The micro-galvanic effect was negligible at pH 1 but enhanced as the pH increased from 7 to 13 (Cu and W were cathode and anode respectively). The micro-galvanic effect can be observed from the electrochemical tests, but the actual influence involving kinetics can be observed realistically from the immersion test.
Nano-crystalline single phase bce solid solution of sputter-deposited tungsten-rich W-Nb alloys are passivated spontaneously in all hydrochloric acid solutions examined, and their corrosion rates are dependent upon the concentration of HCl solutions at 30 degrees C. The corrosion rate of the tungsten-rich W-Nb alloys in 12 M HCl is lower than that in 6 M HCl, although the initial corrosion rate measured for less than about 24 h in 12 M HCl is higher than that in 6 M HCl. XPS and AFM results reveal that the more aggressive nature of 12 M than 6 M HCl solution enhances fast formation of more stable and protective passive films, consisting of tungsten-rich double oxyhydroxide of tungsten and niobium ions due to fast dissolution of niobium. This is responsible for higher corrosion resistance in 12 M HCl than that in 6 M HCl solution at 30 degrees C. (C) 1998 Elsevier Science Ltd. All rights reserved.
High-melting metals belong to transitional metals that are characterised by strong atomic bond in crystal lattice and thus by high-melting temperatures, high strength and heat resistance. These metals considerably surpass other metallic structural materials by their absolute strength level and relative strength (ratio of ultimate strength to density). High corrosion resistance in concentrated acids and some physical properties of high-melting metals, such as high electric resistance, high electron emissivity, etc. also belong to their sought-after properties.
The sintered microstructure of potassium doped P/M tungsten is besides the usual residual porosity characterized by small nanosized spherical potassium filled bubbles in the diameter range between 10 and 50 nm. During the deformation of the sintered ingots the spherical bubbles change their morphology into elongated bubble tubes or ellipsoids. At intermediate annealings these potassium tubes decay above critical dimensions due to Rayleigh instabilities into rows of spherical bubbles which determine the recrystallization and the high temperature–low stress creep behaviour of doped tungsten wires. For a correct description of the occurring shape changes the relative density of the tungsten ingots at the beginning of the deformation steps as well as the deformation temperature and the temperature–time regime of intermediate annealings must be considered. In addition, there are significant differences between bubble sizes and bubble numbers located in the grain volume and at grain boundaries. For the occurrence of single bubbles a mechanism of “in situ spheroidization” during deformation will be proposed. Further reasons for discrepancies between experimental and modeled bubble dimensions at high true strains of deformation will be discussed.
A study has been made of the corrosion of metals which form the basis of high temperature alloys in an argon-25%H2-10%HCl-5%CO-1%CO2 gas mixture at 900°C. The aim has been to ascertain the possible importance of the formation of volatile chloride-containing species of these metals in the degradation of alloys under similar conditions. Considerations of the thermodynamics of the system enable the chlorine, oxygen and carbon potentials of the mixed gas to be ascertained and thus the possible reactivity of the metals to be estimated. The situation is complicated by the development of phases with high vapour pressures. Thus, iron is corroded rapidly due to the formation of FeCl2. The chlorides of nickel and cobalt are less volatile and, hence, these metals undergo much less corrosion. Chromium is able to form a Cr2O3 scale in this environment but penetration of chlorine-containing species to the metal-scale interface enables liquid chloride phases to develop and disrupt further the protective scale. Molybdenum and tungsten are reasonably inert in the gas mixture.
By means of the “interruption kinetic technique”, as applied to oxidation of tungsten under 0.048 bar O2, the oxygen diffusion coefficient in growing WO8−x has been determined for the temperature range of 568–908°C and may be expressed as: D = 6.83 × 10−2 exp (−29,890/RT), with the activation energy given in cal/mole. Calculations are made to show the influence of temperature on the concentration of oxygen vacancies in WO3−x, on their free energy of formation and on the ionic conductivity in WO3−x. From the kinetic data of W oxidation at 800°C, prior to interruption-annealing, values of oxygen diffusion coefficients due to oxygen transport via lattice and short-circuit paths have been calculated as functions of time for growing WO3−x. A simplified oxidation model is used for evaluation of the oxidation rate constant of W at 800°C.
The formation and dissolution of the anodic oxide film of tungsten were investigated in sulphuric acid solution of different concentrations. The dissolution process was found to follow a first order mechanism under different conditions. It seemed that, in highly diluted solutions, the hydrate formation is favoured, whereas in concentrated solutions, the process takes place via the formation of WO22+. The rate of dissolution was found to increase by increasing the initial current density of formation.
Chemical reactions of tungsten with steam which persist to tungsten temperatures as low as 800°C result in the formation of a hydrated tungsten-oxide which has a high vapor pressure and is readily convected in a flowing atmosphere. The vaporization reaction removes the oxide scale that forms on the tungsten surface as it forms, leaving behind a fresh metallic surface for further oxidation and vaporization. Experiments were conducted with cylindrical tungsten rods heated to temperatures from approximately 700°C to 1350°C in flowing steam which was superheated to 140°C to measure the oxidative vaporization rates of tungsten in steam. The results of these experiments revealed a threshold temperature for tungsten vaporization in steam between 700°C and 800°C. Other tests were conducted over the temperature range of 800–1350°C. In these tests, the tungsten rods were found to have lost weight due to vaporization of the tungsten and the missing weight was collected in the downstream condensate system. The aerosol formed a fine white smoke of tungsten-oxide which was visible to the eye as it condensed in the laminar boundary layer of steam which flowed along the surface of the rod. The aerosol continued to flow as a smoke tube downstream of the rod, flowing coaxially along the centerline axis of the quartz glass tube and depositing by impaction along the outside of a bend and at sudden area contractions in the piping. The vaporization rate data from 17 experiments which exceeded the vaporization threshold temperature are presented. Two correlations to the present data are presented and compared to a published correlation in the literature [7].
The compatibility of rotary swaged tungsten and sodium was investigated at 500, 600, 700°C, and also at 600°C of polished tungsten. The weight loss curves for the two kinds of W-specimens appear significantly different, however their weight losses approach constant values after testing for 400h. The asymptotic change in sodium containing 30μg/g oxygen at 600°C are about 2.3 and 0.8mg/cm2 from 400 to 1500h, respectively for the rotary swaging tungsten and the polishing tungsten. The corrosion products at the surfaces of two kinds of W-specimens after testing in high temperature sodium are different. The grains show significant growth after testing of both kinds of tungsten. The fracture stress of the rotary swaged tungsten at room temperature decreases considerably after testing with the effect slightly increasing with temperature from 500, 600 to 700°C. A much smaller decrease of fracture stress is observed for polished tungsten at 600°C, which already before testing has much smaller value. The micro-morphologies of the fracture surface indicate brittle inter-granular fracture in both kinds of tungsten. Embrittlement becomes much more notable for rotary swaged tungsten, while inter- and trans-granular fracture modes appear after corrosion tests in high temperature sodium for both kinds of tungsten.
The chlorination kinetics of tungsten, molybdenum, and three of their binary alloys have been studied as part of a Bureau of Mines effort to provide information of value when considering chlorine metallurgy processes. Tungsten and molybdenum were used for this initial investigation of alloys because they are chemically similar, form a complete range of solid solutions, and have been shown to chlorinate at temperatures sufficiently different so as to facilitate the determination of temperature dependency of reactivity by experiments based on the measurement of weight loss as the volatile chlorides are formed. Both the pure metals and alloys containing 22, 48, and 72 atomic per cent (a/o) molybdenum were found to chlorinate between 400° and 775°C at rates of 10⁻⁷ to 10⁻⁵ mole per square centimeter per minute, with the reaction rate dependent upon the 0.6 power of chlorine pressure. Molybdenum exhibited the highest reactivity, tungsten was the least reactive, and the alloys showed intermediate reactivity with respect to temperature. Single crystals of the pure metals showed marked anisotropy upon chlorination. When chlorinated, the polycrystalline alloy specimens of 22 and 72% molybdenum tended to show the crystalline anisotropy exhibited by the major component, while the 48% molybdenum specimen developed no pattern similarity to the pure metals.
Galvanostatic anodization of W has been studied in 10N solutions of HCl, H2SO4, HNO3, H3PO4, and HClO4 at 30°C. Experimental factors including electrode pre-treatment, stirring, acid concentration, temperature, open circuit decay, and cathodic polarization have been investigated in detail. The valve-metal behaviour of W is evident in all acids, and the electrode suffers but little from anodic dissolution. At constant c.d., the rate of oxide formation increases in the order HClO4, H3PO4, HNO3, H2SO4 and HCl, and increases with increase in c.d. The simple theory of anodization is applied, and data are given for reciprocal capacity, electrolytic parameters, activation distance, electric field, and pre-polarization thickness. The spark potential depends on the nature of electrolyte.
The performance of structural materials in lead or lead-bismuth eutectic (LBE) systems is evaluated. The materials evaluated included refractory metals (W, Mo, and Ta), several U.S. steels [austenitic steel (316L), carbon steels (F-22, Fe-Si), ferritic/martensitic steels (HT-9 and 410)], and several experimental Fe-Si-Cr alloys that were expected to demonstrate corrosion resistance. The materials were exposed in either an LBE rotating electrode or a dynamic corrosion cell for periods from 100 to 1000 h at temperatures of 400, 500, 600, and 700 deg. C, depending on material and exposure location. Weight change and optical scanning electron microscopy or X-ray analysis of the specimen were used to characterize oxide film thickness, corrosion depth, microstructure, and composition changes. The results of corrosion tests validate the excellent resistance of refractory metals (W, Ta, and Mo) to LBE corrosion. The tests conducted with stainless steels (410, 316L, and HT-9) produced mass transfer of elements (e.g., Ni and Cr) into the LBE, resulting in degradation of the material. With Fe-Si alloys a Si-rich layer (as SiO{sub 2}) is formed on the surface during exposure to LBE from the selective dissolution of Fe.
The kinetics of the anodic oxidation of tungsten metal in basic aqueous solution has been investigated using galvanostatic
polarization. Anodic Tafel slopes were constant over all concentrations of hydroxide at 0.136 V/decade. Cathodic Tafel slopes
ranged from 0.069 to 0.197 V/decade, increasing with hydroxide ion activity. Anodic exchange current density, obtained by
extrapolation, averaged
. Single ion activities, estimated by Harned's rule, in sodium hydroxide solutions buffered with sodium nitrate to constant
ionic strength, yielded rate data indicating first‐order dependence on hydroxide ion activity over a concentration range of
0.02–6.00M OH−. A mechanism commensurate with the observed behavior is proposed involving oxidation to intermediate tungsten oxides, followed
by nonelectrochemical dissolution to form the soluble tungstate anion. A brief discussion of the data for the hydrogen evolution
reaction is also presented, in the light of recent studies on tungsten covered by oxide layers.
Tungsten-based alloys have been used in a wide variety of industrial and military applications. These alloys are composed mainly of tungsten (88–95%) with various combinations of nickel, cobalt, iron and copper usually making up the remaining fraction.The corrosion behaviours of five munitions grade tungsten alloys of interest have been examined using immersion tests and wet-dry cycle tests to determine the mechanisms involved in the release of the metallic components. Analyses carried out using SEM, EDS and grazing incidence XRD techniques, show the release of tungsten as well as alloying elements due to galvanic corrosion resulting from the difference in electrode potential between the tungsten phase and the binder phase in all cases studied. The extent of corrosion was directly related with the dissolution of tungsten in the binder phase during the sintering stage of manufacture. In W–Ni–Co–Fe alloys binder phase corrosion was observed while the relatively noble tungsten phase was less affected. The reverse was observed for a W–Cu alloy.
This study was performed to determine the in vitro degradation rate of tungsten coils and to evaluate the potential local toxicity of tungsten on human pulmonary arterial endothelial (EC) and smooth muscle cells (SMC) and human dermal fibroblasts (FB). Therefore, tungsten coils were immersed in Ringer's solution and loss of mass and increase in tungsten concentration in the electrolyte were assessed in relation to immersion time (maximum: 140 days). Primary cultures of EC, SMC and FB were grown on multiplates for 1-10 days with ascending concentrations (0.1-5000 microg/ml) of tungsten in the growth medium. Metabolic activity was assessed by the use of the WST-1 Test (Roche). The in vitro degradation rate of the tungsten coil was 29 microg/day. EC were most susceptible to tungsten with a LD50 of 50 microg/ml. In contrast, the LD50 for SMC was 100 and 1000 microg/ml for FB after 10 days of incubation. We conclude that, in vitro, degradation rate of tungsten coils is slow (29 microg/day). Very high (>50 microg/ml [normal serum value 0.0002 microg/ml]) tungsten concentrations are needed to result in local cytopathologic effects on human EC, SMC and FB. These results correspond to clinical observations demonstrating the absence of toxicity of degrading tungsten coils in adult and pediatric patients despite elevated serum tungsten levels.
Tungsten Sources, Metallurgy, Properties, and Applications
- S W H Yih
- C T Wang
"Tungsten Sources, Metallurgy, Properties, and Applications", S.W.H. Yih and C.T. Wang;
Chemo-mechanical polishing and electrochemistry of tungsten using mixed oxidisers with hydrogen peroxide and ferric nitrate
"Chemo-mechanical polishing and electrochemistry of tungsten using mixed oxidisers
with hydrogen peroxide and ferric nitrate", Yom-Jan Seo, Nam-Hoon Kim, Woo-Sen Lee,
Materials Letters, 60, 1192-1197 (2006)
On the electrochemical behaviour of tungsten: formation and dissolution of tungsten oxide in sulphuric acid
"On the electrochemical behaviour of tungsten: formation and dissolution of tungsten
oxide in sulphuric acid", M.S. El-Basiouny, S.A. Hassan, M.M. Hefny, Corrosion Science, 20,
909-917 (1980)
Influence on concentration of HCl solution on the passivation behaviour of sputterdeposited tungsten-rich W-Nb alloys
"Influence on concentration of HCl solution on the passivation behaviour of sputterdeposited tungsten-rich W-Nb alloys", J. Bhattarai, E. Akiyama, H. Habazaki, A. Kawashima,
K. Asami, K. Hashimoto, Corrosion Science, 40, 1897-1914 (1998)