The chemistry and electrochemistry associated with the electroplating of group VIA transition metals

White, S. H.; Twardoch, U.M.

doi:10.1007/bf01023289

Cited by 48 publications

(27 citation statements)

References 28 publications

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“…Usually, Mo, W, Mo 2 C, and W 2 C coatings are deposited onto non-oriented metal substrates by electrolysis of Na 2 WO 4 -based oxide melts [1][2][3][4]. However, in many instances it is necessary to obtain continuous cathode deposits with preset properties (structure, orientation, and crystallite size).…”

Section: Introductionmentioning

confidence: 99%

Initial stages of nucleation of molybdenum and tungsten carbide phases in tungstate–molybdate–carbonate melts

2007

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The electrochemical nucleation of Mo 2 C and W 2 C crystals for tungstate-molybdate-carbonate melts of specific compositions on Ag, Au, Cu, Pt, and Ni substrates was studied by the electrodeposition method. The influence of electrocrystallization conditions (temperature, deposition time, initial current pulse, and current density) was investigated. Experimental measurements indicate that crystallization overvoltage is associated with threedimensional nucleation. Carbide deposition onto the substrates prepared from the same solid materials was not associated with crystallization overvoltage. The maximum value of the initial overvoltage, g max , which includes crystallization and electrolysis overvoltages, is proportional to the electrode surface area. Under these conditions, surface diffusion limits the electrode process rate. An increase in carbide deposition rate leads to an increase in the number of crystallization centers. This reduces the duration of surface diffusion. A rise in the melt temperature complicates the crystallization process by alloy-formation phenomena. Overvoltage maximum height for metals, which do not form alloys, is proportional to the reciprocal of their formation time. Melt temperature increase promotes interdiffusion of refractory metal, carbon, and substrate, and also intensifies their chemical interaction. Structural mismatch is observed during molybdenum and tungsten carbide electrodeposition onto different singlecrystal substrates.

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Section: Introductionmentioning

confidence: 99%

Initial stages of nucleation of molybdenum and tungsten carbide phases in tungstate–molybdate–carbonate melts

2007

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“…One of the early works carried out by White and Twardoch [30] determined the eutectic melting point of the LiBr-KBr-CsBr salt to be 236°C. However, they have not reported details of the measurement procedure.…”

Section: Determination Of the Melting Point Of Eutectic Libr-kbr-csbrmentioning

confidence: 99%

“…That is why, these melts have been used for metal deposition/coating studies. White and Twardoch [30] could obtain coherent chromium coatings from the LiBr-KBr-CsBr-CrBr 2 melt in the temperature range 300-450°C. They have observed that unlike in a NaCl-KCl melt (where the chromium reduction was found to be reversible, requiring both lower chromium content in the bath, 2-5 mol%, and cathode current density, 0.025-0.05 A cm −2 ), due to the lower diffusion rate of the chromium in the ternary bromide melt it became easier to obtain smooth and coherent chromium coatings on copper, nickel and steel substrates.…”

Section: Introductionmentioning

confidence: 99%

Aluminum electroplating on steel from a fused bromide electrolyte

Tripathy

Wurth²,

Dufek

et al. 2014

Surface and Coatings Technology

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A quaternary bromide bath (LiBr-KBr-CsBr-AlBr 3 ) was used to electro-coat aluminum on steel substrates. The electrolyte was prepared by the addition of AlBr 3 into the eutectic LiBr-KBr-CsBr melt. A smooth, thick, adherent and shiny aluminum coating could be obtained with 80 wt.% AlBr 3 in the ternary melt. The SEM photographs of the coated surfaces suggest the formation of thick and dense coatings with good aluminum coverage. Both salt immersion and open circuit potential measurement suggested that the coatings did display a good corrosionresistance behavior. Annealing of the coated surfaces, prior to corrosion tests, suggested the robustness of the metallic aluminum coating in preventing the corrosion of the steel surfaces. Studies also indicated that the quaternary bromide plating bath can potentially provide a better aluminum coating on both ferrous and non-ferrous metals, including complex surfaces/geometries.Published by Elsevier B.V.

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IntroductionReviews on studies concerning chemistry and electrochemistry of tungsten in melts were made in contributions [1][2][3][4]. Methods of tungsten electrodeposition from aqueous, aqueous-organic and organic solutions have not found any practical application because deposit quality and technique complexity do not satisfy manufacturing requirements.

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mentioning

confidence: 99%

Codeposition of Silver with Tungsten Carbide in Tungstate Melts

Малышев

Gab²,

Gaune‐Escard

2007

ECS Trans.

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Diffusion controlled one-electron reversible electroreduction of silver in tungstate melts was established by voltammetric and potentiometric methods, and Ag + ions effect on electrodeposition of tungsten carbide coatings was studied. IntroductionReviews on studies concerning chemistry and electrochemistry of tungsten in melts were made in contributions [1][2][3][4]. Methods of tungsten electrodeposition from aqueous, aqueous-organic and organic solutions have not found any practical application because deposit quality and technique complexity do not satisfy manufacturing requirements. We have also investigated recently the electrodeposition of tungsten and its carbide in tungstate-carbonate melts [5][6][7].The electrochemical behavior of silver was studied in ionic melts of different composition. High reversibility of silver electrode with respect to Ag + ions was established and used in reference electrodes [1]. The one-electron reversible reduction of silver ions in zinc chloride and alkali chlorides melts was proven, and decomposition of oxygen-containing silver compounds at high temperatures accompanied by silver metal formation was noted. Silver reference electrode was also used in molten tungstates, but its behavior in such media, particularly in tungstate-molybdate systems, is not yet completely understood. ExperimentalExperiments were conducted in air using platinum crucible as anode and as container. Reagents were analytically pure sodium tungstate and reagent-grade tungsten (VI) oxide. Silver tungstate was prepared by precipitation from mixture of water solutions of AgNO 3 and Na 2 WO 4 and identified by XRD analysis. Reference electrode was the Pt, O 2 | Na 2 WO 4 -0.2 WO 3 half-cell separated from melt by alundum diaphragm [1,5,6]. Indicator electrodes were submerged platinum and edge silver electrodes. The latter ones were preparated by silver metal melting in alundum tube 1.5 mm wide. Experimental setup consisted of stainless steel reactor inside a resistor furnace and of the analytical Radiometer Voltalab PST 050 apparatus for measuring current-potential curves. ECS Transactions, 3 (35) 423-428 (2007) 10.1149/1.2798686, copyright The Electrochemical Society 423 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 155.69.4.4 Downloaded on 2015-05-31 to IP 424 Results and discussionTwo waves are observed in voltammograms for Na 2 WO 4 -WO 3 -Ag 2 WO 4 melts at -(0.3-0.5) V and -(1.2-1.3) V. (Fig.1). The first wave corresponds to the reduction of Ag + ions to metallic silver, the second one corresponds to the reduction of W 2 O 7 2-ditungstate ions to tungsten metal. Potentiostatic electrolysis at the first-wave potential produces silver metal. The following changes occur in the current-potential curves at increasing Ag 2 WO 4 concentration: the silver deposition potential is shifted by about 400 mV towards positive values; the W 2 O 7 2-reduction wave potential is shifted from -(-1.2-1.3) V to -(0.4-0.5) V. Due to electrodepos...

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The chemistry and electrochemistry associated with the electroplating of group VIA transition metals

Cited by 48 publications

References 28 publications

Initial stages of nucleation of molybdenum and tungsten carbide phases in tungstate–molybdate–carbonate melts

Initial stages of nucleation of molybdenum and tungsten carbide phases in tungstate–molybdate–carbonate melts

Aluminum electroplating on steel from a fused bromide electrolyte

Codeposition of Silver with Tungsten Carbide in Tungstate Melts

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