Electrodeposition of cobalt from gluconate electrolyte

Cobalt electrodeposited onto steel substrate was carried out from solutions containing cobalt sulfate, boric acid and sodium gluconate. The study dealt with the influence of bath composition, current density, pH and temperature on the potentiodynamic cathodic polarization curves, cathodic current efficiency, and throwing power, as well as the throwing index of these baths. The microhardness of cobalt electrodeposited from gluconate baths is generally high and higher than that of cobalt deposited under similar conditions from sulfate, chloride, bromide and acetate baths. The surface morphology of the as-deposited cobalt was investigated using scanning electron microscopy (SEM) while the structure was studied using X-ray diffraction analysis. Cyclic voltammetric, as well as current-transient, techniques recorded on a glassy carbon electrode suggested that the deposition of cobalt from gluconate bath occurs via a nucleation process under charge transfer control.     

Nucleation and growth of tin on low carbon steel

The nucleation and growth of tin from stannous sulfate and sulfuric acid with an organic additive of gelatin was studied on low carbon steel. Investigations were conducted by linear sweep voltammetry and current step methods. The agitation effect on the morphology of tin deposits was also studied. From the results, a mechanism of tin deposition on a steel substrate is suggested. Initially, 3D tin crystallites are formed preferentially on step edges, and this is followed by fast covering of neighboring sites with much smaller and densely packed crystallites of about 150-180 nm in size. Without gelatin, the coverage was poor and tri-modal structures were dominating. It is discovered that the synergy between hydrogen co-evolution and gelatin contributes to fast and complete coverage of the steel substrate and the bi-modal grain size distribution is observed. The diffusion coefficient of tin ion was determined according to the Sand equation.     

Effect of additives on electrodeposition of tin and its structural and corrosion behaviour

The present investigation deals with the electrodeposition of tin from chloride electrolytes. Gelatin, β-naphthol, polyethylene glycol, peptone and histidine were used as additives in the plating bath to improve the surface morphology, grain size, smoothness and corrosion resistance of the tin deposits. XRD data obtained for electrodeposited tin show polycrystalline nature with single β-phase and tetragonal structure. A uniform and pore free surface was observed under SEM analysis. AFM results indicate the grain refining brought about by the additives. Corrosion rate measurements using the Tafel extrapolation method and electrochemical impedance spectroscopy reveal the increased corrosion resistance from baths containing additives.     

Magnetic properties of nanocrystalline iron group thin film alloys electrodeposited from sulfate and chloride baths

Systematic studies of iron group binary (NiCo and CoFe) and ternary (CoNiFe) thin film alloys relating their magnetic properties with film composition, grain size and the corresponding crystal structure were investigated. Anions influence current efficiencies, magnetic properties, surface morphology and phases of electrodeposited films. Higher current efficiencies in chloride baths compared to sulfate baths were observed for CoFe, NiCo and CoNiFe alloys. The higher deposition current efficiencies in chloride baths were attributed to a catalytic effect. Anion types in CoFe and CoNiFe thin film alloys influenced the microstructures and the resulting magnetic properties (coercivity and squareness). The microstructures of NiCo alloys depend on the deposit Co contents rather than anion types. The surface morphologies of CoFe, NiCo and CoNiFe thin films were independent of anion types. CoFe deposits exhibited relatively smooth surface morphology and turned into fine crystallites with increasing solution Fe⁺² concentration. NiCo deposits showed very smooth surface morphology. CoNiFe deposits had the surface morphology of polyhedral crystallites. The deposit Fe content in CoFe electrodeposits linearly increased with increasing solution Fe⁺² concentration for both chloride and sulfate baths. Similar linear behavior of deposit Co contents was observed in NiCo electrodeposits.     

Electrodeposition of Sn-Co alloys from gluconate baths

Electrodeposition of Sn-Co alloys was carried out from baths containing 2–20 g dm^–3 SnSO₄, 4–18 g dm^–3 CoSO₄.7H₂O, C₆H₁₁O₇Na and K₂SO₄ under different conditions of bath composition, pH, current density and temperature on to copper substrates. The influence of these variables on the cathodic potential, cathodic current efficiency and composition of the deposit were studied. The results show that the deposition of Sn-Co alloys from gluconate baths depends greatly on the concentration of tin. At high tin concentrations, tin is the more noble component. At low tin concentrations, tin reduction is strongly suppressed due to the formation of a more stable Sn-gluconate complex species and tin becomes the less noble component. The codeposition of Sn-Co alloy from these baths can be classified as an irregular plating system. The surface morphology of deposits was examined by scanning electron microscopy and crystal structure by X-ray. The results show that the structure of the deposits was controlled by the alloy composition.     

电沉积无铅可焊性锡铋合金的研究

提出了一种酸性锡铋合金电沉积工艺。研究了镀液中硫酸铋含量和电流密度对镀层铋含量、电流效率及镀层表面形貌的影响，另外，通过循环伏安曲线的测量研究了锡铋合金的电沉积过程，结果表明，镀层铋含量随硫酸铋含量的增大而增大，铋在-0.3V时开始析出，当电位达到-0.6V时，锡和铋共同沉积。     

Effect of electrolysis factors on crystal orientation and morphology of electrodeposited cobalt

Cobalt electrodeposition was carried out using sulfate and chloride baths to investigate the effects of electrolysis factors on the crystal orientation and morphology of the deposits. The preferred orientation of Co deposited from the sulfate baths changed from (0 0 0 2) to (1 1 0) plane with an increase in the deposition overpotential and the deposits showed the largest grain size with a smooth surface in the low overpotential region. On the other hand, no dependence of crystal orientation and morphology on deposition overpotential was found in chloride baths.     

Study of copper electrodeposition mechanism from a strike alkaline bath prepared with 1-hydroxyethane-1,1-diphosphonic acid through cyclic voltammetry technique

Copper strike baths are extensively used in metal plating industry as they present the ability to plate adherent copper layers on less-noble metal substrates such as steel and zinc die castings. However, in the last few years, due to environmental controls and safety policies for operators, the plating industry has been interested in replacing the toxic cyanide copper strike baths with environmentally friendly baths. A broad bibliographic review showed that the published papers, referring to the new nontoxic copper strike baths, are patents, having little or no emphasis focused on electrodeposition mechanisms. Therefore, it was decided to study the copper electrodeposition mechanism from a strike alkaline bath prepared with one of the most nontoxic chelating agents cited in many patents which is the 1-hydroxyethane-1,1-diphosphonic acid, known as HEDP. This acid forms very stable water soluble complexes with Cu²⁺ ions, thus cupric sulfate was used for preparing the plating bath. The results obtained through a cyclic voltammetry technique showed that Cu²⁺ ion reduction to Cu from an HEDP electrodeposition bath occurs via a direct reduction reaction without a formation of Cu⁺ intermediates.     

Electrodeposition of copper into trenches from a citrate plating bath

The electrodeposition of copper from a citrate solution has been investigated as a function of pH of the plating bath, and applied to the filling of 500 nm trenches. Speciation diagrams of copper in aqueous citrate solution were used to select four deposition baths with different dominant copper-citrate complexes, which was corroborated using UV–vis spectrophotometry. The electrochemical properties of the plating baths were determined in order to relate the deposition kinetics to the morphology of deposits in trenches. SEM images illustrate that the plating bath at pH 3.1, where only mild inhibition of the deposition kinetics is observed, is capable of adequately filling the trenches.     

Role of polyethylene glycol in electrodeposition of zinc–chromium alloys

The role of polyethylene glycol (PEG) as an additive in the electrodeposition of zinc–chromium alloys was investigated in sulfate baths containing trivalent chromium. PEG with high molecular weight enabled the codeposition of metallic chromium with zinc, while chromium(III) was present in the deposits obtained from the baths containing PEG with lower molecular weight as well as the PEG-free bath. The polarization curves for the alloy deposition revealed that PEG with high molecular weight polarized the deposition potential of zinc to the reduction potential of chromium to permit the codeposition of chromium with zinc.     

Tin–cobalt electrodeposition from sulfate–gluconate baths

The electrodeposition of tin + cobalt alloys from a slightly acidic sulfate–gluconate bath on both vitreous carbon and copper substrates has been studied for different [Sn(II)]/[Co(II)] ratios in the bath, varying between 1/10 and 1/2. A relationship between the electrochemical stripping analysis and the morphology of the deposits has been found. Two different types of deposit were obtained. At low [Sn(II)]/[Co(II)] ratios and relatively high deposition rates a nodular, cobalt-rich, nanocrystalline coating was obtained, while at high [Sn(II)]/[Co(II)] ratios and low deposition rates a new, well-defined tetragonal SnCo phase was obtained, with cell parameters of a = 3.087 Å and c = 5.849 Å. This structure favours hydrogen evolution.     

Characterising nonuniform electrodeposition and electrodissolution using the novel wire beam electrode method

An electrochemically integrated multi-electrode system namely the wire beam electrode (WBE) has been applied as a new method of characterising nonuniform electrodeposition and electrodissolution, by measuring and identifying characteristic patterns in electrodeposition and electrodissolution current distribution maps. Various patterns of electrodeposition current distribution have been obtained from Watts nickel plating and bright acid copper plating baths with the effects of several affecting factors such as bath concentration, temperature, agitation and electrolyte flow. Typical patterns of electrodissolution current distribution have also been detected over a WBE surface under anodic dissolution. This work suggests that the WBE method can be used as a new tool for monitoring, characterising and optimising electrodeposition and electrodissolution processes in the laboratory, and can also be applied as an experimental method to verify the accuracy and completeness of mathematical models for electrodeposition and electrodissolution.     

Electrodeposition of Pb–Cu alloy coatings from gluconate baths

Pb–Cu alloy coatings were electrodeposited on steel sheet cathodes from baths containing mixtures of lead nitrate, copper nitrate and sodium gluconate. Cathodic polarization, cathodic current efficiency and deposit composition were determined under different plating conditions. The results were consistent with the behaviour of a regular plating system with copper being the preferentially depositable metal. The lead (the less noble metal) content in the deposits increased with increase in current density and concentration of lead in the bath but decreased with increase in bath copper concentration. The structure and morphology of the as-deposited coatings were examined by X-ray, AES and SEM. The results showed that the deposits consist of a mixture of fine crystals of the two metals and the morphology of the deposits is mainly controlled by the composition of the deposit.     

Study of the effect of mannitol on ZnNi alloy electrodeposition from acid baths and on the morphology,composition, and structure of the deposit

A boric acid bath for ZnNi alloy electrodeposition was developed with mannitol as additive. The deposition process was investigated by cyclic voltammetry. It was found that the current density decreased, due to adsorption of a boric–mannitol complex and/or changes in the morphology, but the initial deposition potential was not affected. At deposition potentials more negative than −1.20 V, the current efficiency obtained was high (80–85%) in all baths studied. The addition of mannitol to the bath led to the formation of the best ZnNi deposits, composed of coalesced globular grains smaller than ~1 μm in diameter. Also, all of the ZnNi deposits studied consisted of γ, γ₁, and Pt₃Zn phases. The Ni content in the ZnNi deposits produced in the presence of mannitol increased from 6 to 10 wt% only in the range −1.26 to −1.40 V. It is suggested that the ZnNi deposits produced in these baths probably offer sacrificial protection to the substrate.     

Zn-Ni合金电沉积过程中的渗氢行为

用电化学渗氢测试方法探讨了氯化物体系、硫酸盐-氯化物混合体系电沉积Zn-N i合金镀层过程中的渗氢行为。结果表明,氯化物体系比硫酸盐-氯化物混合体系渗氢电流小,用电镀过程中的氢覆盖率和镀层孔隙率对渗氢特点进行了解释。     

Effect of aromatic aldehydes on the electrodeposition of ZnCo alloy from cyanide-free alkaline-gluconate electrolytes

The effects of vanillin and anisaldehyde on electrodeposition of zinc–cobalt alloys onto AISI 1018 carbon steel were studied in an alkaline gluconate zincate electrolyte. The influence of an additive on the metal discharge depends on the structure of the added molecule and on the nature of the substrate. The composition of the deposit varies during the electrodeposition process. Maximum cobalt content is observed close to the steel–ZnCo interface for ZnCo formed with or without vanillin, but the composition profile becomes more uniform when anisaldehyde is added to the bath. The morphology of Zn-rich Co-alloy coatings was evaluated: Cobalt ions produce porous ZnCo alloys; vanillin induces slightly porous deposits, whereas uniform and more compact deposits were observed with anisaldehyde. Furthermore, a crystallographic study showed that the orientation of the lattice planes changes, with highly oriented deposits produced in the presence of anisaldehyde.     

Electrodeposition of Zn–Mn alloys in acidic and alkaline baths. Influence of additives on the morphological and structural properties

Electrodeposition of Zn–Mn alloys on steel was achieved using alkaline pyrophosphate-based baths or acidic chloride-based baths. Cyclic voltammetry was used to determine the potential ranges where the various redox processes were taking place. It appeared that the reduction of Mn(II) was generally hidden by the other reduction reactions, especially by the hydrogen evolution reaction. Zn–Mn alloys containing up to 25 at.% Mn in the alkaline bath and 12 at.% in the acidic bath could be obtained at the cost of very low current efficiencies. The characterisation of the deposits obtained either by galvanostatic polarisation or potentiostatic polarisation was performed by Scanning Electron Microscopy and X-Ray Diffraction. Various Zn–Mn phases were obtained, depending on the current densities, the composition of the deposit and that of the electrolytic bath. Two commercial additives usually used for zinc electrodeposition, one in alkaline baths, the other in acidic baths, were tested. Their effects upon the composition, the morphology and the microstructure of the deposit were investigated.     

锡及锡合金可焊性镀层电镀工艺

介绍了目前常用于电子元器件电镀纯锡液的主要技术要求。阐述了酸性硫酸盐镀锡、酸性氟硼酸盐镀锡或锡-铅合金、烷基磺酸盐镀锡或锡-铅合金、中性或弱酸性镀锡或锡-铅合金的工艺特点、镀液镀层性能及性价比。还介绍了Sn—Bi、Sn—Ag、Sn—Cu无氟无铅可焊性电镀锡基二元合金的特点、性能及典型的工艺配方。     

BH-411光亮硫酸镀锡工艺及实践

介绍了BH-411光亮硫酸镀锡的工艺配方、工艺流程和镀液的维护与管理,讨论了镀液中的硫酸、硫酸亚锡和添加剂的作用。中试实验结果表明：使用BH-411光亮硫酸镀锡工艺,所得镀层结晶细致、光亮,与基材的结合力良好,可焊性能好,抗变色性强该工艺可以在生产中推广使用。     

Anodic linear sweep voltammetric analysis of Ni–Co alloys electrodeposited from dilute sulfate baths

Anodic linear sweep voltammetry was used to characterise electrodeposits of Ni, Co and five Ni–Co alloys (5:1, 2:1, 1:1, 1:2 and 1:5 ratios) obtained in a potentiodynamic mode on a vitreous carbon electrode from dilute sulfate baths. The voltammetric results showed a complex behaviour, with the deposits strongly dependent on the metal ion concentrations and less dependent on the final deposition potential. Probably due to simultaneous hydrogen evolution, the efficiency of the electrodeposition (in sulfate baths) and electrodissolution (in ammoniacal bath) processes of pure Co and Ni–Co alloys decreased with increasing final potential in all solutions, while that of pure Ni was enhanced with a shift to more negative potentials. Morphological information was acquired through investigations by techniques such as SEM, EDX and dot mapping. The voltammetric results revealed solid solution characteristics, with profiles varying from pure Ni to pure Co. The results of semi-quantitative EDX chemical analyses suggest a regular deposition mechanism instead of an anomalous one as is often observed in such binary systems.