Electrodeposition of lead–tin alloy from methanesulphonate bath containing organic surfactants

The article discusses the process of electrodeposition of lead-tin alloy (tin content in the deposit up to 10–12 wt %) from methanesulfonate electrolytes. A composition was proposed of organic additives to the electrolyte providing attainment of high quality microcrystalline coatings with the alloy of predetermined composition at relatively low content of Sn²⁺ in the solution. It has been shown that the tin content in the deposit increases at an increase in current density and decrease in the electrolyte temperature. For production of anti-frictional Pb-Sn alloys with the tin content of about 10% the electrolysis should be performed at a current density of about 4 A/dm² and the temperature not exceeding 25°C. The effect of a decrease in the discharge rate of the Sn²⁺ ions into the alloy at deposition from electrolyte without organic additives was discovered, that is stipulated by deceleration of crystallization stage of tin on foreign substrate. When the alloy is deposited from electrolyte containing a composition of organic additives, the effect of super-polarization of discharge of Sn²⁺ ions is reduced.     

Characterization of Zinc-Cobalt Electrodeposits

The structure and morphology of electrodeposits depend on many factors including temperature, current density, time of deposition and composition of the bath. The properties of an electrodeposit depend on its micro structure. For example corrosion and wear resistance, hardness, internal stress, strength, brightness, electrical conductivity, magnetic properties and leveling are all affected by structure.

The relationships between electroplating parameters such as current density, temperature, bath agitation and electrolyte composition have been investigated for the zinc-cobalt system. It was found that electrolyte composition and temperature affect both deposit composition and morphology. The cathodic current efficiency decreased with current density and hardness was raised with increasing cobalt content in the deposit.

Three powerful techniques were used to access the microstructure of zinc-cobalt deposits: scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that the alloy is constituted of a single phase of a solid solution of cobalt dissolved in zinc within an hexagonal crystal system. The deposit is porous and changes from dendritic to nodular with increasing cobalt content.     

Electrodeposition and properties of an iron-tungsten alloy

Iron-tungsten alloys were obtained from citrate electrolytes. The relation between Fe(II) and Fe(III), which permits maintaining the stability of an electrolyte as well as obtaining high-quality deposits for a long time, is revealed. The results of investigations show that the discharge of iron ions takes place from the three valent ions. It is found that the concentration of sodium tungstate in the electrolyte contributes to the codeposition of tungsten, increasing its ratio in the alloy. It is established that the current efficiency and composition of iron-tungsten coatings depend on the current density and the conditions of electrolysis. The microhardness of iron-tungsten deposits increases with an increase in the deposition temperature and depends on the tungsten content in the alloy. Investigations with an electron microscope have shown that, on the alloy surface, superficial inhomogeneous films with the content of tungsten and oxygen different from that in the deposit are formed. The obtained alloys have concentration and structure inhomogeneities.     

Methods for controlling the composition and morphology of electrodeposited Fe–Mo and Fe–Co–Mo coatings

The effect of the electrolyte composition and the stationary electrolysis parameters on the composition and morphology of Fe–Mo and Fe–Co–Mo coatings deposited from complex citrate electrolytes based on Fe(III) is studied. It is shown that, at a constant component ratio of с(Fe³⁺): с(Co²⁺): с(MoO^2? ₄): с(Cit^3–) = 2: 2: 1: 4, an increase in the electrolyte concentration leads to a decrease in the pH of the solution in a range of 4.85–4.30 and in the molybdenum content in the coating. An increase in the current density contributes to the molybdenum enrichment of the electrodeposited alloy in the entire range of electrolyte concentrations. The Fe–Mo alloy coatings have a rough microporous surface; an increase in the current density does not lead to significant changes in the surface topography. It is found that the formation of ternary coatings is characterized by the competitive reduction of iron and cobalt in the alloy; the molybdenum content depends on the current density. At a metal ratio of 3: 2: 1 and a molybdenum content of up to 17 at % in the Fe–Co–Mo alloy, the surface has a fine-grained needlelike structure typical of cobalt. With an increase in i _c, the atomic fraction of molybdenum increases, while the surface becomes microglobular. The Fe–Co–Mo electrodeposits with a metal ratio of 2.5: 1.5: 1.0 and a molybdenum content of 19–20 at % have a more developed surface with a high density of spheroids.     

A Study into the Electrodeposition Mechanisms of Zinc-Nickel Alloys from an Acid-Sulphate Bath

Zinc-nickel alloys were electrodeposited under galvanostatic conditions from a sulphate based electrolyte. The effect of deposition current density on alloy composition was determined for an electrolyte containing 0.58 mol/l nickel and 0.92 mol/l zinc (as sulphates). At current densities exceeding 0.01 A/dm², a transition from normal deposition to anomalous co-deposition (ie where the less noble metal deposits preferentially) was observed and alloys rich in zinc were obtained. The transition current density was observed to increase with an increase in electrolyte temperature or a decrease in electrolyte pH.

The electrodeposition mechanism for zinc-nickel alloys in the transition regions was studied in detail using potentiodynamic cathodic polarisation techniques. The results were consistent with the suppression of nickel deposition due to the precipitation of zinc hydroxide on the cathode surface. This was supported by pH measurements made in the vicinity of the cathode where a rise in pH was detected as the transition current density was approached and exceeded the critical pH for zinc hydroxide precipitation.     

Amorphous Cobalt-Boron Alloy Electrodeposition and Dissolution

Co-B alloy has been deposited on steel from an alkaline citrate bath. Uniform deposits have been obtained in the current density range of 8–15 Adm ^?2.Cvclic voltammetric studies on platinum from this bath reveal that the cobalt citrate complexes undergo stepwise electronation with the participation of hydroxyl ions. The borates undergo reduction to boron in the alloy deposition. The hydrogen evolution reaction has been found to be hindered by cobalt and borate ions. Stripping voltammetric curves on the alloy film suggest the dissolution of cobalt from a cobalt rich phase.     

Estimation of the protective ability of chromium coatings deposited from sulfate and methanesulfonate electrolytes based on Cr(III)

Voltammetric and impedance techniques are used to determine the protective ability of chromium coatings deposited on a steel substrate from sulfate and methanesulfonate electrolytes based on trivalent chromium. It is found that chromium deposits obtained from methanesulfonate electrolyte have lower porosity and higher protective ability as compared with deposits from sulfate electrolyte. It is shown that, when the thickness of chromium coatings reaches 15 μm, there are no through pores in deposits for both electrolytes and, thus, the maximum degree of protection of the steel support is achieved in an aggressive medium. An equivalent circuit correctly modeling the corrosion-electrochemical behavior of the studied system is proposed on the basis of data of electrochemical impedance spectroscopy, and the values of its parameters are calculated.     

钴含量对电铸镍钴合金模芯微纳结构复制质量的影响

为探明电铸液中钴含量对仿荷叶表面镍钴合金模芯微纳结构复制质量的影响,采用阴极竖直旋转的微电铸技术,制备不同钴含量的仿荷叶表面镍钴合金模芯,采用扫描电子显微镜（SEM）、能谱仪（EDS）分析仿荷叶表面镍钴合金模芯表面的复制质量及成分。结果表明：由于铸层表面内应力的影响,在常规镍电铸中添加钴以后,仿荷叶镍钴合金模芯表面出现了波纹型的褶皱;观测模芯微观形貌发现其表面微米级的孔洞沿特定方向出现不同程度的拉伸,随着电铸液中钴含量（体积分数）的增加,拉伸程度先增加后降低（拉伸程度：钴含量0 g/L<钴含量40 g/L<钴含量10~30 g/L）;铸层中添加元素钴有利于晶粒细化,随电铸液中钴含量的增加,模芯表面微纳结构越细小,复制质量越高。     

Composition and structure of arsenic–antimony alloy electrodeposited from acidic chloride solution

AsSb alloy (0.70–95.81 wt.% As) was prepared by electrodeposition in As(III) and Sb(III) contained electrolytes. The influence of electrolyte composition, hydrochloric acid concentration, and temperature on the composition and structure of AsSb deposits was studied. The electroreduction mechanism of As(III) and Sb(III) in hydrochloric acid solution was revealed via thermodynamic analysis. The results show that the increase of H⁺ concentration promotes the reduction of As(III), while the increase of Cl⁻ concentration significantly inhibits the reduction of Sb(III). As a result, the As content in deposits increases gradually with the increase of hydrochloric acid concentration. Simultaneously, the phase structure of AsSb deposits evolves from crystalline to amorphous. When the As content is 24.55–33.75 wt.%, AsSb mixed crystal is obtained. The electrolysis temperature has little effect on the deposits composition, but the structure of deposits evolves from crystalline to amorphous with decreasing the temperature.     

Electrodeposition and mechanical properties of Ni-W-B composites from tartrate bath

Electrodeposition of Ni-W-B alloys from plating baths containing tartrate in the absence of ammonia is studied. Detailed studies on the effects of bath temperature, pH, cathode current density and plating time have led to optimum operational conditions for obtaining satisfactory alloy deposits. The operational conditions for deposition the alloy with high hardness are; current density 30 mA cm^?2, pH 6.0 and bath temperature of 60°C. The results have shown that the adherence of Ni-W-B is better than the Ni and Chromium on Cu substrate. It adheres to Cu substrates better than electrodeposited Ni and chromium. The morphology of the deposits was studied by SEM and the analysis of composition performed by EDX and inductively coupled plasma (ICP). The as-deposited alloy contained 21.66 wt % W and the highest cathode current efficiency for deposition of the alloy was about 38%. The deposit obtained under these conditions had an amorphous character with a hardness of about 800 HV, which is comparable to the hardness of chromium, occurred at a heat treatment temperature of 400°C. When heat treated up to this temperature, the initial metastable structure decomposed into fine particles of Ni₄W in a nickel solid solution.     

Studies on the Electrodeposition of Ternary Copper-Zinc-Tin Alloys

The colour of Cu-Zn-Sn alloy coatings obtained by electrodeposition may differ-white, gold, dark gold, pink, and so on—depending on the specific combination of deposition conditions such as electrolyte composition, temperature, pH value and current density. Effects of pH and current density on the colour of the deposits and the associated electrode processes at the cathode and anode during deposition have been investigated. It was found that increasing either pH or current density causes an increase in the Zn content of the deposit and results in a colour trend away from pink and towards yellow. It was also found that cathodic deposition takes place in the sequence Sn, Cu, Zn, followed by Cu-Zn-Sn alloy. Anodic dissolution occurs at—1.0 V. From this study a reproducible gold-coloured coating was achieved, which could be of considerable practical importance.     

Effect of electrolyte pH and Cu concentration on microstructure of electrodeposited Ni-Cu alloy films

Single Ni and Ni-Cu alloy films were electrodeposited on polycrystalline Ti substrates from electrolytes with different pH values under potentiostatic control. The deposition processes of the films were evaluated by the current-time transients recorded during deposition. The analysis of the transients clearly showed that the initial deposition of Ni is affected by the electrolyte pH, while in the Ni-Cu alloys the Cu concentration of the electrolyte is more effective than the electrolyte pH. The microstructural analysis by X-ray diffraction (XRD) indicated that the texture degree in both Ni and Ni-Cu alloy films, which have face-centered cubic (fcc) structure, changes with the electrolyte pH. The surface morphology of the samples was investigated using the scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was observed from SEM and AFM studies that the surface roughness of Ni deposits is not considerably affected by the electrolyte pH, while in Ni-Cu alloy films it changes significantly with both the electrolyte pH and the Cu concentration. Accordingly, the surface roughness of the Ni-Cu alloy films increased as electrolyte pH decreased and Cu concentration increased.     

Electrodeposition of Amorphous Iron-Nickel-Phosphorus Alloy Coatings

The effects of plating parameters on the composition and structure of electrodeposited Fe-Ni-P alloys have been studied. A sulfate electrolyte containing sodium hypophosphite with an acetate buffer was used. Deposits were plated onto both planar and rotating cylinder electrodes. Alloy deposits that were amorphous over a wide range of iron:nickel ratios were achieved. The anomalous deposition typical of Ni-Fe alloy plating was not observed in these studies where phosphorus was codedeposited. The deposit composition was dependent on both the plating bath composition and current density.     

On the Electrodeposition of Tungsten-Cobalt Alloys From Aqueous Solutions

Sound coherent deposits of tungsten-cobalt alloys with up to 60–66 wt. % of tungsten can be produced at cathode current efficiencies of up to 21% from solutions containing 40–70 g./l. of tungsten as sodium tungstate, 4–12 g./l. of cobalt as cobalt sulphate, 70–150 g./l. of citric acid and 50 g./l. of ammonium chloride, adjusted to room-temperature pH of 7·5–8·5 with sodium hydroxide, and operated at 50–70° C. with interrupted d.c. pulses of 0·05–2 sees, and equal or rather greater “off” periods, the cathode current density during the pulses being 5–20 amps./dm.². Moderate agitation of the solution is desirable.

Hydrogen overpotential for hydrogen deposition from citrate buffers is much less on tungsten-cobalt cathodes than on tungsten or cobalt cathodes. Evidently the electronic structure of the alloy cathodes is much more favourable than that of tungsten for hydrogen deposition: this suggests that it is also more favourable for tungsten deposition, which may help to explain why tungsten-cobalt alloys are so much more easily deposited than pure tungsten.

A number of amphipathic organic molecules, among them thiourea, benzenesulphonamide and pyridine, increase the hydrogen overpotential on tungsten-cobalt alloys: but they do not increase the cathode current efficiency of alloy deposition, evidently because they increase the metal-deposition overpotential about equally.     

阴极电流密度对6061铝合金在含Na2WO4电解液中微弧氧化膜结构和耐磨性能的影响

目的 研究恒流模式下阴极电流密度对6061铝合金在含Na2WO4的电解液中制备的微弧氧化膜厚度、形貌、相组成及耐磨性能的影响。方法 固定阳极电流密度为5.0 A/dm²,阴极电流密度分别为0、1.25、2.5、3.75、5.0 A/dm²,对6061铝合金进行微弧氧化40 min。用涡流测厚仪测量了氧化膜的厚度,用扫描电镜观察了微弧氧化膜的表面形貌和截面形貌,用能谱分析仪分析了氧化膜的表面成分,用X射线衍射分析仪分析了微弧氧化膜的相组成,用往复式摩擦磨损试验机测试了氧化膜的耐磨性能。结果 随着阴极电流密度的增加,氧化膜内的W含量逐渐减少,氧化膜颜色逐渐变浅,氧化膜厚度逐渐增加。微弧氧化膜的主要组成相为α-Al2O3和γ-Al2O3。当阴极电流密度从0 A/dm²增加到3.75 A/dm²时,氧化膜内孔洞的数量和尺寸逐渐减少,孔洞到氧化膜/基体界面的距离逐渐增加,氧化膜的耐磨性能逐渐提升。当阴极电流密度为3.75 A/dm²时,氧化膜的磨损率最低,仅为1.07×10^‒4 mm³/(N.m)。但阴极电流密度增加到5.0 A/dm²时,氧化膜表层出现孔洞和剥落,耐磨性能下降。结论 阴极电流的加入有助于增加6061铝合金微弧氧化膜的厚度,提高氧化膜的致密性和耐磨性能,但过高的阴极电流会导致氧化膜表层出现孔洞,降低耐磨性能。     

Effect of bath composition and pulse electrodeposition condition on characteristics and microhardness of cobalt coatings

Nanocrystalline cobalt coatings were produced from cobalt sulfate based electrolytes by using pulse current electrodeposition technique. The effects of bath composition and electrodeposition condition on current efficiency, morphology, structure and hardness of the coatings were investigated and the optimum deposition condition was determined. It was found that increment of cobalt sulfate concentration and sodium dodecyl sulfate (SDS) concentration in the bath had a negligible effect on microhardness of the coatings, while they were effective on electrodeposition current efficiency. Adding saccharin to electrodeposition bath decreased crystallite size of hexagonal close-packed (hcp) cobalt films and increased their microhardness without significant effect on current efficiency. Smoother and less defective coatings were also obtained from baths containing SDS and saccharin. The results revealed that both the current efficiency and microhardness were changed by variation of peak current density and duty cycle. Besides change of smooth morphology of the coatings to needle-shaped one, crystallite sizes and preferred orientation also varied with increasing the current density and duty cycle.     

Properties of ‘Sulpho-Chromispel-I’ electrolyte of standard concentration for the electrodeposition of chromium

The most important properties of non-standard highly efficient “Sulpho-Chromispel- I” type electrolytes for chromium plating have been investigated. They contain as side anions catalysing the cathodic process, both SO^2-₄ and I^?. The effects of cathodic current density and concentration of hydroiodic acid on the total current distribution are evaluated. The deposition rate is determined. The effect of operating parameters on the throwing power is established. The properties of the electrolytes studied are compared with those of standard sulphate electrolytes and “Chromispel-I” compositions. The most efficient electrolyte comprises CrO₃:I- = 20:1 and 20 cm³ dm^?3 sulphuric acid. The deposition rate can reach a value of 250 μm h^?1 at a current density of 200 A dm^?2. The throwing power of this electrolyte is close to that of standard sulphate electrolytes. As a whole “Sulpho-Chromispel-I” electrolytes exhibit lower throwing power compared to standard sulphate electrolytes or pure “Chromispel-I” electrolytes. They are recommended for chromium plating details of simple profile.     

Electrodeposition of Zn-Co and Zn-Co-Fe alloys from acidic chloride electrolytes

The electrodeposition operating conditions for Zn-Co and Zn-Co-Fe alloys from chloride baths were studied. The electrodeposition was performed on a high strength steel substrate, under galvanostatic conditions, for a range of current densities at varying Co²⁺ and Fe²⁺ bath concentrations and at different temperatures. A transition current density was noticed above which a transition from normal to anomalous deposition took place. Below the transition current density electrodeposition of alloys with a higher amount of Co was obtained. Above the transition current density (i.e. in the anomalous range), both Zn-Co and Zn-Co-Fe alloys were deposited with a Co content lower than the composition reference line. This transition current density that resulted in normal to anomalous deposition was attributed to the shift in cathodic potential or polarization. However, it was found that under certain conditions the transition occurred from very high wt.% Co to almost equal to the amount of Co in the electrolyte. The increase of Fe²⁺ ions in the electrolyte assisted in increasing the Co content and decreasing the Zn content in the deposits. In addition, the increase of Fe²⁺ resulted in shifting the transition current density to a lower value. However, the cathodic current efficiency decreased with the addition of Fe²⁺ ions in the electrolyte.     

Studies on electrochemical deposition of novel Zn–Mn–Ni ternary alloys from an ionic liquid based on choline chloride

Ternary Zn–Mn–Ni alloy coatings were electrodeposited for the first time from a choline chloride based ionic liquid with the aim of collecting properties of binary Zn–Mn and Zn–Ni alloys into one alloy system. The effect of electrodeposition potential on the composition and corrosion performance of the obtained ternary Zn–Mn–Ni deposits was investigated and contrasted with the characteristics of Zn–Mn and Zn–Ni deposits. Cyclic voltammetry revealed that the deposition of ternary Zn–Mn–Ni alloys behaved differently from the deposition of binary Zn–Mn and Zn–Sn alloys and that Mn deposition takes place at positive potentials in the Zn–Mn–Ni electrolyte than in the Zn–Mn electrolyte due to the presence of Ni²⁺ ions in the electrolyte. X-ray diffraction studies showed that the Zn–Mn–Ni ternary alloys consist of a lattice of Zn (with Mn and Ni imbedded inside) at low electrodeposition potentials and MnZn(with Ni imbedded inside) phase at high electrodeposition potentials. Chemical composition analysis show that the Mn content in the ternary Zn–Mn–Ni alloy increased with increase in electrodeposition potential, whereas Zn and Ni contents are suppressed. The corrosion tests results indicate that through addition of Ni into the Zn–Mn binary alloy, the Zn–Mn–Ni alloy tailored are more corrosion resistant than the Zn–Mn binary alloy whilst the passivation behavior is still preserved.     

The Structure of Electrodeposited Nickel

Here are presented the results of laboratory studies on various types of acid rhodium plating electrolyte, with particular reference to sulphate and phosphate-sulphate solutions, but including exploratory trials on phosphate, fluoborate and sulphamate electrolytes. The sulphate electrolyte is preferred for general purposes.

For the first two electrolytes, examination is made of the effects of variations in preparative procedure on the characteristics of electrolytes of the same nominal composition, and the influence of composition and deposition factors on the internal stress of deposits.

Factors affecting the incidence of cracking of thick rhodium deposits are discussed, and on the basis of laboratory and field experience, practical recommendations are made concerning the formulation of sulphate electrolytes and the optimum operating conditions for the production of rhodium deposits in the thickness range 0·002-0·002” from this type of solution. Procedures are detailed for either the rhodium or silver/rhodium plating of the basis metals most commonly involved in industrial applications.