Sulfate-chloride Electrolyte Research Articles

Electrochemical Deposition and Properties of Ni Coatings with Nitrogen-Modified Graphene Oxide

In this study, a method for producing nitrogen-modified graphene oxide (NMGO) using hydrothermal synthesis in the presence of triethanolamine is presented. The composition and structure of NMGO are characterized using X-ray phase analysis (XPA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and Raman spectroscopy. Ni-based metal matrix coatings (MMCs) modified with NMGO were obtained from a sulfate-chloride electrolyte in the galvanostatic mode. The process of electrochemical deposition of these coatings was studied using chronovoltammetry. The microstructure of Ni–NMGO MMCs was studied using the XPA and SEM methods. It has been established that the addition of NMGO particles into the Ni matrix results in an increase in the microhardness of the resulting coatings by an average of 1.30 times. This effect is a consequence of the refinement of crystallites and high mechanical properties of NMGO phase. The corrosion-electrochemical behavior of studied electrochemical deposits in 0.5 M sulfuric acid was analyzed. It has been shown that the corrosion rate of Ni–NMGO MMCs in a 3.5% sodium chloride environment decreases by approximately 1.50–1.70 times as compared to unmodified Ni coatings. This is due to NMGO particles that act as a barrier preventing the propagation of the corrosion and form corrosive galvanic microelements with Ni, promoting anodic polarization.

Electrolytic coating of iron-chromium alloy of sulphate-chloride electrolyte in machine parts recovery process modelling

Introduction. The technological process of restoring a part should provide more than 80% of the resource and no more than 50% of the cost of a new part. The wear resistance of the applied coating determines the resource of the restored part operating under waterjet and boundary friction. The microhardness of an iron-based electrolytic coating is one of the key indicators of wear resistance. The study of the results of statistical processing and the factors most affecting the increase in the microhardness of the iron-based coating will make it possible to recommend and optimize the deposition conditions for obtaining the most wear-resistant coatings.Materials and methods. The studies on equipment that let to obtain the necessary data with the required accuracy were carried out. The mathematical processing using modern statistical data processing tools that excluded possible errors, let to obtain the dependence of factors with the necessary accuracy was carried out.Results. During the study of the developed sulfate-chloride electrolyte for the deposition of an iron–chromium coating, it became necessary to determine the effect of deposition conditions – ‘factors’ (temperature, acidity of the electrolyte, cathode current density) on the microhardness of the coating – ‘response’. It was found that the combination of the factors ‘temperature’ and ‘cathode current density’ in the coded values of 1.5. 2.0 and -2 are the most significant. The deposition conditions in order to obtain a coating with maximum microhardness are optimized.Discussion and conclusions. As a result of the conducted studies for the effect of the deposition conditions of the Fe-Cr alloy from the sulfate-chloride electrolyte on the microhardness of the coating, it was found that in order to obtain high-quality coatings of the iron-chromium alloy with high microhardness, it is necessary to strictly comply with the requirements of the deposition conditions and acidity to a greater extent. As the current density and temperature of the electrolyte, compared with the acidity of the electrolyte, iron baths are installed and regulated by equipment.

Pulsed Electrodeposition and Properties of Nickel-Based Composite Coatings Modified with Graphene Oxide

Composite electrochemical coatings (CECs) on the basis of nickel modified with multilayer graphene oxide (GO) were deposited from a sulfate–chloride electrolyte in pulsed electrolysis mode. The microstructure of these CECs was studied by X-ray phase analysis and scanning electron microscopy. It was found that the microhardness of nickel–GO CECs increases by approximately 1.40 times compared to pure nickel. The corrosion–electrochemical behavior of nickel–GO composite coatings in 0.5 M H2SO4 was studied. Based on tests in 3.5% NaCl, it was found that the addition of graphene oxide particles into the matrix of nickel electrodeposits, increases their corrosion resistance by 1.40–1.50 times. This can be explained by the uniformity of the distribution of GO in the nickel matrix, which contributes to the reduction in grain size, as well as the impermeability and stability of graphene oxide.

Lightweight macroporous Co-Pt electrodeposited films with semi-hard-magnetic properties

Macroporous, partially L10-ordered Co-Pt films with nearly equiatomic composition were successfully synthesized by electrodeposition from an aqueous sulfate–chloride electrolyte on colloidal crystal-templated substrates, followed by annealing in vacuum. The colloids deposited on the substrate consisted of amidine-functionalized polystyrene spheres of 215 ± 13 nm in diameter, which were self-assembled by electrophoresis. As-deposited Co-Pt films obtained after the removal of the spheres showed a highly-packed arrangement of macropores. Structurally, the films showed the A1-disordered face-centered cubic (fcc) Co-Pt solid solution, accompanied by small amounts of fcc/hexagonal close-packed (hcp)–Co. Upon annealing at 600 °C, the A1-disordered phase partly transformed into the L10-ordered (face-centered tetragonal, fct) phase. As a result, the coercivity significantly increased from 148 Oe to 1328 Oe. Importantly, the porosity of the films was preserved after annealing. Optimum annealing temperature and time were selected on the basis of a prior parametric study with electroplated dense counterparts. This work demonstrates that the combination of colloidal crystal templating and electrodeposition is a very convenient pathway towards lightweight semi-hard magnets with potential technological applications in automotive and aerospace industries, portable sensors or spectrometers, magnetic levitation systems, or magnetoelectric devices, among others.

Co-Ni alloy coatings electrodeposited using real leachates generated from positive electrodes of Ni Cd batteries

The feasibility to recover a Co Ni alloy is evaluated in the present study by electrodeposition using real liquors from the leaching of Ni Cd batteries (positive electrodes) in H 2 SO 4 , with saccharin as additive. Ni content in the alloy rises with increasing the applied current density for all baths, while current efficiencies higher than 70% are achieved with the use of the sulfate-chloride electrolyte containing saccharin. The additive could strongly interact with chloride to suppress the occurrence of parasitic reactions (H + and H 2 O reductions), while the formation of chlorocomplexes particularly of Ni(II) accelerate their reduction on the electrode surface. This mixed electrolyte also enables to obtain more pure Co Ni alloys at −600 A m −2 , as detected in the analysis of O composition (5.12 at.%/1.36 wt%). The impurities favorably affected the contributions of both parasitic reactions. Saccharin predominantly blocks H 2 O reduction at high overpotential, but not H + discharge at low overpotential. The particle size and shape of the alloys strongly rely on current density imposed and bath composition. All deposits contain Cd, although its content is considerably less favored as the current density is increased to −600 A m −2 . XRD confirms the microstructure of the formed alloys, mainly comprised of the following planes: Ni(111) and Co(111), CoOOH(003) and Cd(OH) 2 (001). • Ni content in the alloy rises in all baths as current density is increased. • Sulfate-chloride electrolyte with saccharin presents the highest current efficiency. • Metal chlorocomplexes reduce faster than sulfate species on electrode surface. • Cd content is considerably decreased at high current density for real baths. • Alloy texture strongly depends on current density and bath composition.

Electrodeposition and Corrosion Properties of Nickel-Graphene Oxide Composite Coatings.

Nickel-based composite electrochemical coatings (CEC) modified with multilayer graphene oxide (GO) were obtained from a sulfate-chloride electrolyte in the reverse electrolysis mode. The microstructure of these CECs was investigated by X-ray phase analysis and scanning electron microscopy. The corrosion-electrochemical behavior of nickel–GO composite coatings in a 0.5 M solution of H2SO4was studied. Tests in a 3.5% NaCl solution showed that the inclusion of GO particles into the composition of electrolytic nickel deposits makes their corrosion rate 1.40–1.50 times less.

Electrolytic alloying of iron-chromium during deposition of coatings from a sulfate-chloride electrolyte

The paper presents the results of studies of the process of electroreduction of alloy iron-chromium from a sulfate-chloride electrolyte, influence of electrolyte composition and electrolysis (acidity, electrolyte temperature and cathode current density) on the process kinetics, the output of the alloy current efficiency and physico-mechanical properties of the coatings (microhardness, morphology). There were determined such parameters as the optimal ratio of concentrations of electrolyte components – 150 g/l of iron chloride (2) and 50 g/l of chromium sulfate (3) and modes of electrical recovery of metals – current density 40 A/dm2; the temperature of the electrolyte is 50°C, the acidity of the solution is 0.5 pH units, which contribute to obtaining a high-quality coating with high tribological characteristics. Assumptions are made about the mechanism of the alloy formation by electrolysis from a mixed electrolyte.

On the Electrochemical Deposition and Properties of Nickel-Based Composite Coatings

Nickel-based composite electrochemical coatings (CECs) modified with graphite nitrate have been obtained. Their microstructure and functional properties (sliding friction coefficient and protective ability) have been studied. It has been found that when a dispersion of graphite nitrate is introduced into a sulfate–chloride electrolyte for nickel plating, the sliding friction coefficient of the formed CECs decreases by half, and the range of potentials of the passive state of these composite coatings increases by 1.26–1.32 times.

Effect of saccharin on corrosion resistance of bright Ni coatings under conditions simulating a wet tropical climate

Corrosion behavior of bright nickel coatings, deposited from sulfate-chloride electrolytes with addition of saccharin and without it, has been studied. The addition of saccharin at a concentration of 5 g/l to a bright nickel-plating electrolyte causes an increase in the content of sulfur in the deposit structure up to 0.25 wt %. The corrosion rate of nickel deposits with the corresponding content of sulfur in acetic acid vapour and dilute acetic acid has been shown by 1-2 orders of magnitude greater than that of deposits containing 0.049 wt % of sulfur obtained from solutions without saccharin. This work suggests that the corrosion rate of nickel coatings is connected with the effect of the content of sulfur in the deposit structure on the adsorption of acetic acid on their surface. A synergetic effect of chloride ions on the corrosion of nickel deposits in the acetic medium has been established.

THE INVESTIGATON OF PHYSICAL AND MECHANICAL PROPERTIES OF NI-P COATINGS / NI-P DANGŲ FIZIKINIŲ IR MECHANINIŲ SAVYBIŲ TYRIMAS

The parameters of electrolytic synthesis of Ni-P coatings on steel surface from sulfate-chloride electrolyte have been determinated. The Ni-P alloys consist of separate phases of Ni and Ni3P and solid solution of implementation on the basis of the FCC Ni lattice, when it was deposited from the electrolyte at current density to be more than 7 A/dm2. The coating was formed with continuous globular surface at current density of 5 A/dm2. The globular formations are the Ni3P phase. The obtained at current density of 9 A/dm2 coatings have maximum value of micro¬hardness 430 HV. Darbe buvo nustatyti Ni-P dangų ant plieno paviršiaus elektrolitinės sintezės (iš sulfatinio-chloridinio elektrolito) parametrai. Ni-P lydinių mikrostruktūrą sudaro atskiros Ni ir Ni3P fazės arba nikelio kietasis įterpimo tirpalas, turintis kubinę paviršiaus centruotą gardelę, kai dangos yra nusodinamos iš elektrolito, esant srovės tankiui daugiau negu 7 A/dm2. Kai srovės tankis yra daugiau negu 5 A/dm2, formuojasi ištisinis, rutulinio pobūdžio dangos paviršius. Rutulio formos darinius sudaro Ni3P fazė. Dangos, turinčios didžiausią mikrokietumo reikšmę 430 HV, gautos esant srovės tankiui 9 A/dm2.

Electrodeposited Ni–Co–B Alloy Coatings: Preparation and Properties

Ternary Ni–Co–B alloys with boron content up to 27 at% were electrodeposited from sulfate-chloride electrolyte containing sodium decahydro-closo-decaborate as a boron source, and the effect of the boron content on the structure, morphology, corrosion, mechanical and magnetic properties of the alloy coatings was studied. With increasing the boron content the structure of the alloys is changed from polycrystalline to amorphous-nanocrystalline and then to amorphous, and the surface becomes more smooth and uniform. During prolonged corrosion testing in 3.5% NaCl solution the amorphous alloys with high boron content demonstrate a gradual decrease in the corrosion rate due to the formation of a rather compact film of the corrosion products consisting of nickel-cobalt hydroxides. In addition, the amorphous Ni–Co–B coatings are less susceptible to the pitting corrosion in comparison with polycrystalline and amorphous-crystalline ones. The boron doping of the Ni–Co alloys improves significantly their mechanical properties. Amorphous Ni–Co–B coatings containing 20 at% B and 10 at% Co demonstrate the highest microhardness and wear resistance. At high content of boron and cobalt, the Ni–Co–B alloys are magnetically soft ferromagnetic materials with high magnetic permeability and low coercivity.

The role of Ni in the surface stability of Cu–Al–Ni ternary alloys in sulfate–chloride solutions

Abstract The stability of Cu–Al–Ni ternary alloys used in the manufacturing of NaCl and Na2SO4 from Lake Qaroun in Egypt was investigated in sulfate–chloride electrolytes. Different electrochemical techniques were used. The results show that the increase in the nickel content improves the stability of the ternary alloys due to formation of a stable barrier film. The barrier film behaves like an ideal capacitor and its stability is affected by the chloride ion concentration. An equivalent circuit model for the electrode/electrolyte interface was proposed and the experimental impedance data were fitted to theoretical data according to this model. The surface morphology and barrier layer constituents were investigated by SEM/EDAX unit.

Anodic oxidation of foil copper on fiber-glass plastic in sulfate-chloride electrolyte

The effect of the conditions of galvanostatic anodizing of copper foil at fiber-glass plastic on growth kinetic parameters of Cu2O films is studied. It is shown that the anodic treatment current density in the sulfate-chloride electrolyte features a logarithmic dependence on the electric field strength in the anodic Cu2O film, which is probably caused by the presence of either a p-n-transition, or an inversion layer of electronic conductivity at the Cu/Cu2O interface. It is found that the dependence of the film thickness on the formation time at different current densities is nonlinear.

Iron coatings from multicomponent methyl sulfate chloride electrolyte

Results of investigations of the influence of the conditions of electrolysis in methyl sulfate chloride (MSC) electrolytes on the hardness, structure, and chemical composition of doped iron coatings are presented. It is found that, by varying the electrodeposition mode, it is possible to obtain coatings with hardness of 4.5–7.2 GPa characterized by fibrous-columnar, granular, and layered structures with a carbon content up to 0.9%, nickel content up to 2–6%, and manganese content up to 2–4%.

Structure and composition of Cu2O films produced by anodizing copper foil on fiberglass laminate

The effect of process conditions on the composition and structure of anodic Cu2O films grown in sulfate-chloride electrolytes has been studied using Auger electron spectroscopy, x-ray diffraction, and atomic force microscopy. The results demonstrate that the copper and oxygen depth profiles in the anodic copper(I) oxide films (ACOFs) are similar in shape. The copper content near the surface is only slightly lower than the bulk copper content. Starting at a depth of 9 nm, the Cu content is constant at an average of 62.7 at %. The Cu2O films grown at a current density j = 3 mA/cm2 have the most perfect stoichiometry, with deviations only in the surface layer. Anodic oxidation produces unoriented polycrystalline films of complex composition. In addition to Cu2O, the films contain CuCl and trace levels of copper. Raising the anode current density influences, for the most part, the formation of (111)-oriented crystallites, changing their orientation from (111) to (220). We assume that nonmetal (oxygen or chlorine) atoms are incorporated into the cubic structure of copper without changing its symmetry but increasing its unit-cell parameter: from 0.3607 (Cu) to 0.426 (Cu2O) and to 0.541 nm (CuCl).

Adhesion of iron coatings with steel and cast iron

The iron-plating process in methyl sulfate chloride electrolytes was investigated. The conditions of iron plating ensuring the coating adherence with steel and pig iron required in the technological processes of reconditioning and strengthening of machine pieces are determined. Process conditions ensuring the high coating adherence with steels 45, 15HGT, 40H, and grey and high-strength pig iron are found; they include steps: powering on of the polarizing current with the initial density of 0.15–0.5 kA/m2 immediately after insertion of pieces in the electrolyte and raising of the current density up to the working level with a rate of 4–5 A/m2 s. Metallographic, polarizing, and other research show the influence of the initial electrolysis conditions on the formation of the first layers of coverings and the process of iron electrocrystallization on structural phases of tempered steel and grey and high-strength pig iron.

ELECTROWINNING OF COBALT FROM A SULFATE-CHLORIDE SOLUTION

Cobalt electrowinning has been proposed as a first step to treat industrial effluents containing significant Co concentrations. In this paper, the effects of various process parameters such as cobalt concentration, electrolyte pH, current density, electrolyte temperature, chloride concentration and electrode spacing on cobalt electrowinning from a sulfate-chloride electrolyte simulating an industrial effluent were studied. Experimental results showed that cobalt concentration had a significant influence on cobalt deposition from this specific system. Current efficiency decreased considerably when the cobalt concentration was reduced to less than 10 g.L-1. The desired cobalt concentration should be greater than 40 g.L-1. Current efficiency decreased with an increase in current density from 100 to 800 A.m-2, while a sharp increase in the current efficiency was noted when the current density was raised from 50 to 100 A.m-2. Generally, the current efficiency increased with an increase in electrolyte pH. In the concentration range studied, the effect of chloride ions on the current efficiency was not significant. Scanning electron microscopy (SEM) examinations of the Co deposits indicated that the above factors have an influence on the structures and surface morphology of the electrowon cobalt. In particular, X-ray diffraction (XRD) studies revealed that the chloride concentration in the solution plays a major role in the preferred orientations of the cobalt deposits.On a proposé l’extraction électrolytique du Co comme première étape du traitement d’effluents industriels contenant des concentrations importantes de Co. Dans ce document, on a étudié l’effet de différents paramètres du procédé, comme la concentration du cobalt, le pH de l’électrolyte, la densité de courant, la température de l’électrolyte, la concentration de chlorure ainsi que l’espacement d’électrode, sur l’extraction électrolytique du cobalt à partir d’un électrolyte de sulfate–chlorure, simulant un effluent industriel. Les résultats expérimentaux ont montré que la concentration de cobalt avait une influence importante sur le dépôt du cobalt à partir de ce système spécifique. Le rendement du courant diminuait considérablement lorsque la concentration du cobalt était réduite à moins de 10 g L-1. La concentration désirable de cobalt devrait être de plus de 40 g L-1. Le rendement du courant diminuait avec une augmentation de la densité de courant de 100 à 800 Am-2 alors qu’on notait une augmentation marquée du rendement du courant lorsqu’on élevait la densité de courant de 50 à 100 A m-2. Généralement, le rendement du courant augmentait avec une augmentation du pH de l’électrolyte. Dans la gamme de concentration étudiée, l’effet des ions chlorure sur le rendement du courant n’était pas important. L’examen au SEM des dépôts de Co a indiqué que les facteurs mentionnés ci-dessus avaient une influence sur la structure et la morphologie de la surface du cobalt extrait par voie électrolytique. En particulier, les études de XRD ont révélé que la concentration de chlorure dans la solution jouait un rôle majeur dans l’orientation préférée des dépôts de cobalt.

On the zinc-nickel alloy electrodeposition mechanism

It is shown that during the zinc–nickel alloy electrodeposition in sulfate–chloride electrolytes, the predominant zinc deposition into the alloy can be caused by the generation of a film in the cathode diffusion layer formed of highly-disperse colloid zinc compounds.

Corrosion resistance of compositionally modulated Zn–Ni multilayers electrodeposited from dual baths

By successive deposition from dual baths containing Zn sulfate electrolyte and Ni sulfate–chloride electrolyte, smooth and bright compositionally modulated multilayered (CMM) coatings with different number, thickness and sequence of the sublayers were obtained. The corrosion resistance of the coatings was studied by anode potentiodynamic dissolution and by corrosion potential measurement. With increase in the number of sublayers, regardless of their individual thickness, the correlation between the quantity of Zn, dissolved at more negative potentials (between −1.250 and −0.750 V vs SSE), and the whole quantity of the metal in the coating, decreases. This correlation is smaller in CMM coatings ending with a Ni oversublayer compared to CMM coatings ending with a Zn oversublayer. The corrosion potentials of CMM coatings ending with a Zn oversublayer composed of a great number thin (0.7 μm) sublayers, are more positive (0.150/0.200 V) than the potentials of CMM coatings composed of a few thick (3.0 μm) sublayers. The most positive corrosion potentials (−0.750/−0.800 V vs SSE) have the CMM coatings ending with a Ni oversublayer; i.e. these multilayered coatings are the most corrosion resistant.

Electrodeposition of Zn–Co alloy coatingsfrom sulfate–chloride electrolytes

The composition, surface morphology and appearance of Zn–Co alloy deposits as a function of current density, electrode potential and Co2+ concentration in the electrolyte was studied. It was found that coatings of good quality with low (1%) Co content are formed at a current density of 0.2Adm−2 and with high (6.5%) Co content at 2Adm−2 from electrolytes containing 1.0M Co2+ under galvanostatic conditions. The potentiodynamic dissolution of coatings with Co content of 6.5% indicates successive deposition of Co enriched phases and a pure Zn phase. The Zn–Co alloys are more corrosion resistant than zinc but are less resistant than cobalt.