汽车零部件锌铁合金滚镀工艺

为适应国家有关淘汰含氰电镀的规定,提出以氯化物锌铁合金电镀工艺替代含氰电镀：某厂汽车零部件滚镀自动线采用锌铁舍金新工艺取代了原氰化滚镀锌工艺：介绍了锌铁合金滚镀工艺及各工序配方,探讨了滚镀液各组分、pH值、阴极电流密度对锌铁合金镀层的影响比较了锌铁舍金滚镀工艺与原氰化工艺的实践应用,表明锌铁舍金滚镀工艺镀层防护性能优、耗电少、生产效率高、成本低,已成功应用于汽车零部件的滚镀自动线。     

电镀锌铁合金工艺

概述了电镀锌铁合金工艺硫酸盐体系、锌酸盐体系、氯化物体系等不同类型镀液及其添加剂 ,如络合剂、表面活性剂、光亮剂和晶粒细化剂。探讨了金属浓度比、pH值、电流密度、温度、脉冲电流对镀层中铁含量的影响 ,并对电镀锌铁合金镀液和镀层性能进行了分析     

电镀锌合金的发展

比较了锌－镍合金、锌－铁合金及锌镀层的性能，指出锌合金钝化膜的高温抗蚀性与二次加工后的抗蚀性比锌镀层有很大提高，介绍了电镀锌－镍合金与电镀锌－铁合金的工艺，并突出介绍其工艺特点，综述了电镀锌合金及其钝化工艺在近年来的发展状况。     

铈对锌-铁合金电沉积的影响

研究了铈对电沉积锌-铁合金镀液及镀层性能的影响,通过分散能力、阴极极化曲线测定,得出在镀液中添加一定量的氯化亚铈能改善镀液性能。通过镀层耐蚀性、抗高温氧化性及镀层表面形貌测试表明,定量铈的参与,可获得更加致密的镀层,可有效提高镀层的耐蚀性及抗高温氧化性。     

清洁生产型锌铁合金电镀工艺

本文综合十多年发表的系列文章,介绍了锌铁合金电镀工艺、水处理、镀液性能和镀层性能。多年的生产实践表明其具有良好的发展前景。     

Microstructural characterization and corrosion resistance of Ni–Zn–P alloys electrolessly deposited from a sulphate bath

Electroless Ni–Zn–P alloy coatings were obtained on an iron substrate from a sulfate bath at various pH values. The effects of changes in bath pH on alloy composition, morphology, microstructure and corrosion resistance were studied. Scanning electron microscopy was performed to observe the morphological change of the deposits with bath pH. Coating crystallinity was investigated by grazing incidence asymmetric Bragg X-ray diffraction and transmission electron microscopy. A transition from an amorphous to polycrystalline structure was observed on increasing the bath alkalinity, and thus decreasing the phosphorus content of the alloys. A single crystalline phase corresponding to face-centred-cubic nickel was identified in the alloys obtained from a strong alkaline solution. An increase in zinc percentage up to 23% in the deposits does not change the f.c.c. nickel crystalline structure. Corrosion potential and polarization resistance measurements indicated that the corrosion resistance of electroless Ni–Zn–P alloys depends strongly on the microstructure and chemical composition. The deposits obtained at pH 9.0–9.5 and with 11.4–12.5% zinc and 11.8–11.2% phosphorous exhibited the best corrosion resistance.     

Zinc–cobalt alloy electrodeposition from chloride baths

Electrodeposition of Zn–Co alloys on iron substrate from chloride baths under galvanostatic and potentiostatic conditions were carried out. Current density, temperature and cobalt percentage in the bath were found to strongly influence the composition of the deposits and their morphology. Changes in potentials, current efficiency and partial current densities were studied. The results show that the shift in potential and in the cobalt percentage of the deposits, for a particular current density during galvanostatic electrodeposition, does not always correspond to the transition from normal to anomalous codeposition. This shift is attributed to zinc ion discharge, which passes from underpotential to thermodynamic conditions. In the range of potentials for the underpotential deposition of zinc, the electrodeposition of zinc–cobalt alloys is discussed, emphasizing the influence of the electrode potential on the composition and microstructure of the deposits.     

Electrodeposition of zinc-nickel alloy coatings: influence of a phenolic derivative

The electroplating of Zn–Ni alloy films from a chloride bath has been studied under different plating conditions, both in the absence and presence of a phenolic derivative. Under the conditions examined, the electrodeposition of the alloys belonged to the anomalous type. The morphology and composition of the deposits varied with current density, temperature, bath composition and additive concentration. The results show that the additive modifies the structure and surface topography of the deposits to a large extent and produces smoother deposits. The corrosion resistance of the alloys has been analyzed by means of salt-spray tests.     

The effects of pulse plating variables on morphology and corrosion behavior of Zn–Fe alloy coatings

Considerable researches have been focused on zinc–iron (Zn–Fe) alloy coatings due to their superior characteristics among zinc alloy electrodeposits in recent years. The corrosion behavior of these coatings depends on the phase structure and morphology of the Zn–Fe deposits. In this work the effects of pulse plating variables such as current density, off-time, frequency and pulse modes on the morphology and phase structure of Zn–Fe deposits was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) analysis. The corrosion behavior of these coatings was measured by means of polarization curves and Neutral salt spray tests. It was shown that pulse reverse coatings exhibit excellent resistance to corrosion in comparison with normal pulse and direct current conditions.     

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.     

Electrodeposition behavior of zinc–nickel–iron alloys from sulfate bath

The present work is directed at collecting the properties of Zn–Ni and Zn–Fe alloys in one alloy via the electrodeposition of Zn–Ni–Fe ternary alloy. Electrodeposition of ternary Zn–Ni–Fe alloy was investigated and compared with the characteristics of Zn–Ni electrodeposits. The electrodeposition was performed from a sulfate bath onto a steel substrate. Structural analysis by X-ray diffraction (XRD) method revealed that the Zn–Ni–Fe alloys consisted of a mixture of zinc, and (γ-Ni₂Zn₁₁) and (Fe₃Ni₂) phases. The study was carried out using electrochemical methods such as cyclic voltammetry and galvanostatic for electrodeposition, while anodic linear polarization resistance and anodic linear sweeping voltammetry techniques were used for the corrosion study. Surface morphology and chemical composition of the deposits were also examined by using scanning electron microscopy and atomic absorption spectroscopy, respectively. It was found that the obtained Zn–Ni–Fe alloy exhibited more preferred surface appearance and better corrosion resistance without adding any organic brighteners to the plating bath in comparison to Zn–Ni alloy that electrodeposited at similar conditions. Results obtained revealed that the increase in corrosion resistance of ternary deposits is not only attributed to the formation of (γ-Ni₂Zn₁₁) phase, but also to iron codeposition and formation of (Fe₃Ni₂) phase.     

Microstructure and corrosion behavior of electroless Ni�CP coatings on 6061 aluminum alloys

The microstructure and corrosion behavior of electroless Ni–P alloy plating on 6061 aluminum alloys substrate in an alkaline plating bath with sodium hypophosphite as reducing agent were investigated. The effects of bath temperature on the plating rate, compositions, and microstructure of the electroless Ni–P deposits were studied. The results showed that the deposition rate and the P content of the electroless Ni–P deposits increased with the rise of the bath temperature. Scanning electron microscopy (SEM) of the deposits showed nodular structure for binary deposits. X-ray diffraction patterns of all the deposits revealed a single and broad peak which indicated the amorphous structure of the deposits. Corrosion resistance of the Ni–P coatings was evaluated by potentiodynamic polarization. The results indicated that electroless Ni–P plating could obviously improve the corrosion resistance of 6061 aluminum alloy.     

Electrodeposition of zinc-cobalt alloy from a complexing alkaline glycinate bath

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.     

Electrodeposition of catalytically active nickel-thallium alloy powders from sulphate baths

The electrodeposition of nickel-thallium alloy powder was investigated from acidic sulphate baths containing 0.0125 NiSO₄·6H₂O, 0.005–0.020 Tl Cl, 0.05–0.23 (NH₄)₂SO₄, 0.1 H₃BO₃ and 0.07 mol l^–1 Na₂SO₄ · 10H₂O. The polarization curves, the percentage composition and the current efficiency of the electrodeposited alloy powders were determined as a function of the bath composition. In addition, some properties of the deposits were examined such as the surface morphology, the structure as revealed by X-ray diffraction analysis and the catalytic activity towards the decomposition of 0.4% H₂O₂ solution. The results indicate that the characteristics of the alloy deposition and the properties of the alloy powder are affected to different extents by the bath composition.     

Influence of a cationic surfactant in the properties of cobalt-nickel electrodeposits

The effect of a cationic surfactant, dodecyltrimethylammonium chloride (DTAC) on CoNi electrodeposition process has been analysed. CoNi electrodeposition is greatly modified by the presence of the cationic surfactant in the bath. The DTAC modifies the initial stages of the deposition process and enhances the cobalt percentage in the deposits. Structure and morphology of the deposits are also modified, as the manner that magnetic properties of the electrodeposited films were affected as a consequence of the structural change. The presence of the surfactant in the bath causes changes on the CoNi structure from face-centred cubic (fcc) to close-packed hexagonal (hcp). DTAC incorporation into the deposits is a function of its concentration in the bath. Thus, it is important to be careful with the effects caused by the surfactant on deposits when it assists the particles insertion.     

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.     

Electroplating of Fe-Ni alloys: Effects of sulphamic acid and sulphosalicylic acid

The electroplating of thin films of Fe–Ni alloys from acidic sulphate baths containing sulphamic acid and sulphosalicyclic acid has been studied under different plating conditions. The alloy composition varied with bath composition, current density and the concentrations of sulphosalicylic acid and sulphamic acid. Stirring of the bath solution enhanced the percentage of Fe in the alloy. The deposition potential became less noble with increase in the current density. Under some plating conditions, the plating system had a cathodic current efficiency greater than 90%. The coercivity values of the alloys were in the range 5–18 oersteds. From the X-ray analysis data f c c structure is assigned to the alloy films. Electroplating conditions have been optimized in order to obtain thin films of 20–80 Fe–Ni permalloy.     

Effect of tartrate on the morphological characteristics of the copper–tin electrodeposits from a noncyanide acid bath

Copper and tin were electrodeposited on platinum substrates from a 1.0 M sulphuric acid plating bath in the presence and absence of tartrate. Voltammetric curves indicated two deposition processes, at –0.310 and –0.640 V, which do not shift upon addition of tartrate to the plating bath. The presence of tartrate decreased the current density in the region of the more cathodic process. The metals were electrodeposited at both deposition potentials and the deposits have the same proportions of copper and tin either with or without tartrate in the plating bath, as observed by AAS. X-ray spectra suggested that a mixture of Cu and -Cu₆Sn₅ alloy was deposited at the less cathodic potential. SEM analysis showed that tartrate affects the morphology of the films.     

次磷酸钠化学镀铜镍合金的研究

研究了以次磷酸钠为还原剂的化学镀铜过程。分析了温度、pH、硫酸镍含量对化学镀铜沉积速率的影响及镀层的表面形貌和结构。结果表明,沉积速率随着镀液温度、pH和N i离子浓度的提高而增大。镀层组分含量和XRD实验结果表明镀层为铜镍合金,呈面心立方结构,晶面间距d与晶胞参数a与标准Cu-N i的相比略大。SEM实验表明,镀层表面形貌为团粒状,颗粒大小较不均匀。     

水溶液中电沉积Ni-La-P合金的研究

含稀土金属的合金具有特殊的功能,常用作电催化材料。由于稀土元素的标准平衡电位较负,在水溶液中很难沉积。因此,采用柠檬酸和氯化铵为混合配位体,硼酸为稳定剂从水溶液中电沉积出Ｎｉ－ Ｌａ－ Ｐ合金镀层。详细介绍了镀液各个组分及工艺条件的选择,获得灰白色、细致的合金镀层。对所得的镀层进行ＳＥＭ 观察和ＸＰＳ分析,结果表明所得镀层为Ｎｉ－ Ｌａ－ Ｐ合金。