共查询到20条相似文献,搜索用时 109 毫秒
1.
2.
The paper describes the results of electrochemical investigations of Ni–Co deposition from a sulfamate bath in the presence of boric acid and two additives. The individual deposition of nickel was shown to be partly inhibited by the adsorption of sulfamate ions at low polarization; such inhibition was not observed for cobalt. The introduction of saccharin at 100 ppm, with a wetting agent seems to hinder sulfamate adsorption and Ni deposition departs at less cathodic potentials. The presence of cobalt has no effect on nickel deposition, whereas cobalt deposition is hindered by the presence of nickel in the bath. Galvanostatic deposition was carried out at the surface of a RDE and with a rotating cylinder Hull cell. At low current densities deposits with a Co content of approx. 40% were produced, but this content was shown to decrease with the applied current density. Examination of experimental data showed that cobalt deposition is diffusion-controlled and that Co content decreases with the applied current density relative to the limiting current density. 相似文献
3.
氨基磺酸体系Co-Ni合金电化学共沉积行为及动力学机理 总被引:2,自引:0,他引:2
通过稳态阴极极化和电化学交流阻抗(EIS)等方法,研究了在不同钴镍金属离子比例的氨基磺酸电解液中,Co-Ni合金的电化学共沉积行为。结果表明在氨基磺酸体系中,导致Co-Ni合金异常共沉积行为的原因和在硫酸盐,或氯化物体系中的不同。不是由于Co^2 抑制了Ni的沉积,而是由于NH2SO3^-作为双齿配体形成的异核络合物在电极表面吸附,阻滞了镍离子的还原过程。并且以晶体场理论为基础解释了Co^2 和NH2SO3^-形成的高自旋络合物,比Ni^2 所形成的络合物具有较高的晶体场稳定化能(CFSE),容易分解。因此吸附在电极表面的氨基磺酸根离子对Co2^2 沉积的阻滞作用小于对Ni2^ 的。这样就导致了在氨基磺酸电解液体系中Co^2 的优先沉积。阳极线性扫描曲线表明.钴镍合金中镍含量越高,沉积层在热力学上越稳定,耐蚀性也越好。同时通过EIS的测试,利用等效电路的分析方法和交流阻抗谱解析理论,提出了氨基磺酸电解液中Co-Ni合金共沉积的动力学机理,较好地解释了实验结果。 相似文献
4.
The role of anion additives in the electrodeposition of nickel-cobalt alloys from sulfamate electrolyte 总被引:1,自引:0,他引:1
Nickel-cobalt alloys have been deposited from sulfamate electrolyte with acetate and citrate-anion additives and evaluated for structure and properties, such as microhardness, tensile strength, internal stress and high-temperature oxidation. XRD data show that at low Co content, the alloys exhibit face-centered cubic (fcc) growth orientations. Above 60% Co, the deposit is completely hexagonal close packed (hcp) with pronounced (100) and (110) lines. It seems likely that the Ni-Co deposits from typical sulfamate electrolyte at pH 5, as well as at current density higher than 5 A/dm2, include metal hydroxides. This is followed by the formation of a more strained structure. The high-temperature oxidation rate of the Ni-Co coating from sulfamate electrolyte at pH 5 is twice that of the alloy deposited from the electrolyte with anion additives. We believe that, citrate complexes of Ni and Co, which are assumed to be involved in alloy deposition, eliminate the incorporation of hydroxides into the deposits and enable low-internal-stress coating. The anion-modified bath offers stability of structure and properties of the alloy over a wide range of acidity and current density. 相似文献
5.
6.
7.
8.
Nanocrystalline Ni–Co alloy coatings containing 0–45 wt% Co were electrodeposited using horizontal electrodes in a modified Watts bath. Different techniques including scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, microindentation, and potentiodynamic polarization were used to characterize the alloy coatings. Properties of the alloy coatings were investigated as a function of the cobalt ion concentration (Co2+) in the bath. It was observed that the alloy codeposition exhibits anomalous behavior. Co content in the alloy coatings increases with increasing Co2+ in the bath and with electrolyte agitation. Morphology and grain size of alloy coatings are greatly affected by Co content. By increasing Co content, surface morphology of the alloy coatings changes from pyramidal to spherical. Microhardness of the alloy coatings increases with increasing Co content mainly due to decreasing grain size that follows the Hall–Petch relation. In addition, Ni–17 wt% Co alloy exhibits better corrosion resistance compared to pure Ni and other Ni–Co alloy coatings. The higher corrosion resistance of Ni–17 wt% Co coating is discussed based on its phase structure, grain size, and preferred orientation. 相似文献
9.
10.
The influence of cobalt chloride concentration, total chloride concentration and sulphate in the electrolyte on cobalt deposition
were studied. The current efficiency increased and the overpotential for electrodeposition of cobalt decreased with increasing
cobalt chloride concentration. Only minor changes were observed with addition of sodium chloride to the cobalt chloride solution.
Sulphate electrolyte resulted in lower current efficiency and higher overpotential for electrodeposition when compared to
a similar cobalt chloride electrolyte. 相似文献
11.
Valéria A. Alves Luís A. da Silva Luís F. de F. Santos Dane T. Cestarolli Alexandre Rossi Leonardo M. da Silva 《Journal of Applied Electrochemistry》2007,37(8):961-969
The electrochemical behaviour of biomaterials based on Cu–Zn–Al (cubic Cu3Zn phase) and Ag–Sn (orthorhombic Ag3Sn and hexagonal Ag4Sn phases) alloys was investigated in carbonate buffer solutions (pH 9.66) in the absence and presence of chloride, using
different electrochemical techniques. Analyses of the open circuit potential and the potentiodynamic polarisation curves showed
that the passivation domain and the corrosion parameters depend on alloy composition and chloride concentration. Chronoamperometric
studies showed that passivation kinetics and corrosion of the passive film are both well described by a linear ln(i) versus ln(t) relation. The passive film formed on the Ag–Sn alloy is less susceptible to corrosion when compared to the Cu–Zn–Al system.
The impedance data obtained in the passive region for the Cu–Zn–Al alloy showed that the passive layer is compact. In contrast,
the impedance data obtained for the Ag–Sn alloy showed that the passive layer is formed by a compact oxide layer covered by
a porous oxide gel layer. Mott–Schottky analysis showed that the passive film formed on the Cu–Zn–Al alloy behaves as a p-type
semiconductor. 相似文献
12.
Electrochemical investigations on the influence of electrolyte composition of Watts baths with special regard to throwing power 总被引:1,自引:0,他引:1
S. Wehner A. Bund U. Lichtenstein W. Plieth W. Dahms W. Richtering 《Journal of Applied Electrochemistry》2003,33(6):457-463
The influence of a variety of substances on technically relevant parameters of a nickel electroplating electrolyte (Watts bath) has been investigated. Special attention has been paid to the throwing power (TP), as well as visual appearance, current efficiency and codeposition of foreign atoms. Systems reported in the literature (e.g., inorganic salts to increase conductivity or complexing agents to increase polarization) were compared with typical reducing agents normally used in electroless Ni deposition. The mechanism of TP improvement in the case of sodium hypophosphite and dimethylamine-borane has been examined with the electrochemical quartz crystal microbalance (EQCM). Using the EQCM it was shown that there is a synergistic effect between the electrochemical and electroless deposition process. In addition, the activation energy of the latter was determined from temperature dependent measurements. 相似文献
13.
In this work, the behaviour of a CoCrMo alloy under simulated body conditions was investigated. More specifically, the electrochemical properties of the alloy and the relevant mechanisms in the passive and transpassive states were studied in detail. Electrochemical techniques such as potentiodynamic and potentiostatic polarisation, cyclic voltammetry, rotating disc electrode and electrochemical impedance spectroscopy were employed. Further, ex situ X-ray photoelectron spectroscopy analysis of the passive films was carried out. A good correlation between the results obtained from all the experimental techniques was achieved. Overall, it was found that the passive film on CoCrMo changed in composition and thickness with both potential and time. The passive behaviour of the CrCrMo alloy is due to a formation an oxide film highly enriched with Cr (≈90% Cr oxides) on the alloy surface. The passive and transpassive behaviour of the alloy is hence dominated by the alloying element Cr. In the transpassive region, strong thickening of the oxide film takes place, combined with a change in the composition of the film, and strongly increased dissolution rate. In the transpassive region, all alloying elements dissolve according to the composition of the alloy. The metal ion release is also very strongly enhanced by cyclic variation of the potential between reducing and oxidizing conditions. In this case, during activation/repassivation cycles, cobalt dissolution is greater than expected from the composition of the alloy. Therefore, active dissolution behaviour is mainly dominated by the alloying element Co. 相似文献
14.
I. Tomov Chr Cvetkova V. Velinov A. Riesenkampf B. Pawlik 《Journal of Applied Electrochemistry》1989,19(3):377-382
The influence of factors affecting the texture formation in zinc coatings electrodeposited from weakly acid zinc baths has been investigated, particularly those of cathodic current density, electrolyte additives and substrate texture type. Deposits showing no preferential orientations were obtained from a chloride bath with no primary inhibitors, with which the earlier theory on autoinhibition caused by colloidal zinc hydroxide in sulphate electrolytes was confirmed. The addition of synthetic inhibitors resulted in the production of various types of texture according to the electrolysis conditions and substrate texture type. Cone fibre texture coatings were obtained on cold worked copper cathodes and at lower cathode densities. A simple fibre texture was produced only at higherD
c values. The preferential orientation of electrodeposited zinc coatings on electrolytic nickel textured substrates depended on whether the electrochemical conditions or the textured substrate was the dominant factor. Various simple fibre textures were formed on electrodeposited amorphous Ni–P alloy substrates irrespective of the electrochemical conditions. Within a relatively short time after the completion of the electrodeposition of zinc coatings from chloride or sulphate baths, recrystallization processes were observed at room temperature. 相似文献
15.
The influence of cobalt on the electrodeposition of zinc onto AISI 1018 steel was studied in weakly alkaline glycine solutions. Thermodynamic calculations were performed to construct predominance-zone diagrams to identify the stability of the zinc and cobalt glycine complexes, and experimental studies of electrochemical behavior and deposit properties were conducted. When zinc is present, cobalt deposition shifts to more negative potentials, producing ZnCo alloys. Two main reduction steps were observed for electrodeposition from the ZnCo bath: the first at low potentials was due to ZnCo electrodeposition. In the second, at more negative potentials, cobalt content in the deposit increased forming a range of intermediate phases, and the hydrogen-evolution reaction became significant. The presence of Co(II) in the bath modified the morphology of the deposits as well as reducing the faradaic metal-deposition efficiency. ZnCo-deposit morphology was modified by the applied current density as well as the metal composition of the coating. X-ray diffraction studies revealed that cobalt oxide or hydroxide is formed during ZnCo electrodeposition, indicating that an elevation of the interfacial pH plays a role in the alloy deposition process. 相似文献
16.
Breakdown of passivity of iron by fluoride occurs locally in weakly acidic and alkaline solutions and generally in strongly acidic electrolytes. The breakdown process occurs in two stages with a first complete removal of the passive layer. HF catalyses the transfer of the Fe3+ ions from the oxide into the electrolyte by a first order mechanism. After XPS analysis the passive layer is thinned and does not contain any fluoride. In the final stage the formation of Fe2+ ions indicates the removal of the passive film. The general attack of the passive layer may be seen as a simpler model for the local breakdown of passive iron by the other halides especially by the technically more important chloride. 相似文献
17.
18.
A systematic study of the corrosion and passivation behaviour of cobalt in aqueous solutions of different pH was carried out. Open circuit potential measurements, polarization experiments and electrochemical spectroscopic (EIS) investigations were employed. The experimental results show that the metal surface is always covered by a native passive film which consists of CoO. The formation of the oxide film obeys a two-electron charge transfer process. The dissolution of the barrier film is controlled by the pH of the solution. In neutral and basic solutions the barrier film is stable. In these media a barrier film thickening with the formation of secondary layer is considered. In acidic solutions, the passive film is unstable and dissolves via a pure chemical process. The mechanism of the corrosion and passivation processes taking place at the electrode/electrolyte interface in the different solutions is discussed. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to confirm the electrochemical measurements and the suggested mechanisms. 相似文献
19.
Electrodeposited Fe group: W and Mo alloys have the potential to replace hard Cr coatings for use in engineering applications where wear and corrosion resistance are needed. Electrochemical studies have concentrated in the past on Ni-W alloy deposition, but now interest in Co-W alloys has developed as they possess lower coefficients of friction when in contact with another metal. The most attractive coating composition is in the range 14-20 at.% W, if controlled deposition promotes crystalline alloys of high hardness, rather than softer amorphous alloys containing >20 at.% W. This paper employs ammonia free baths with low concentrations of cobalt and sodium tungstate and varying additions of sodium gluconate to produce alloys at close to 50% efficiency. Voltammetry, UV and visible spectrometry, and potentiostatic deposition have been performed on such baths, whilst XRD, SEM and TEM observations have been made on the deposits. This aims to optimise the process and to understanding the relationships between bath contents, electrochemical kinetics and alloy composition. Efficient deposition of coatings with hardness values up to 1000 kgf mm−2 occurred from a bath containing a high concentration of gluconate. Such deposits arise from concentrations of Co-W-gluconate complexes which promote the formation of nanoscale alloy grains. Current densities up to 2.75 A dm−2 in the agitated bath promoted deposition kinetics to form these highly orientated structures. These kinetics produced nano-segregation of W which may be assisted by the migration of Co-W clusters to boundary sites during the growth of the deposit. 相似文献
20.
Effect of Zn and Pb as alloying elements on the electrochemical behavior of brass in NaCl solutions 总被引:4,自引:0,他引:4
The electrochemical behavior of brasses with various Zn content (5.5–38 mass%) and brass (Cu–38Zn) with different Pb contents (1–3.4 mass%) in 0.6 M NaCl was investigated. The effects of temperature, immersion time, and concentration of chloride ions on the behavior of the different alloys were studied. The pitting corrosion behavior of Cu–Zn alloys and leaded–brass alloys in 0.6 M NaCl solution was also investigated. Open-circuit potential measurements (OCP), polarization techniques and electrochemical impedance spectroscopy (EIS) were used. The results show that the increase in the Zn content increases the corrosion rate of the brass alloys in chloride solutions, while the increase of Pb content in Cu–38Zn–Pb decreases the corrosion rate of the alloy. Long immersion time of the alloys in the aqueous electrolyte improves their stability due to the formation of passive film on the alloy surface. The breakdown potential is shifted to more negative direction with increasing the Zn content, whereas it shifts towards positive values with increasing Pb content. Equivalent circuit model for the electrode/electrolyte interface under different conditions was proposed to illustrate the electrochemical processes taking place at the interface. The electrochemical behavior of the different alloys was discussed in view of the fitting results. 相似文献