Nickel electrodeposition from novel lactate bath

Abstract

A new electroplating bath for nickel deposition has been developed. Lactic acid was used as a complexing agent in the bath replacing boric acid. The effect of bath composition, current density, pH and temperature on the cathodic polarisation, cathodic current efficiency, morphology and structure of the deposit was carried out. Optimum conditions for producing sound and satisfactory nickel deposits were: 0·30M NiSO₄.7H₂O, 0·50–1·0M lactic acid and 0·3M Na₂SO₄ at pH=10, c.d.=0·98 to 9·80 mA cm^?2 and 25°C. The surface morphology of the deposited nickel was investigated using SEM. The crystal structure was examined by X-ray diffraction analysis. The results showed that the nickel deposits have a face centred cubic structure.     

Mechanism of Nanocrystalline Nickel Electrodeposition from Novel Citrate Bath

用电化学阻抗谱研究了在柠檬酸盐镀液中纳米晶镍沉积的电化学行为,确认了Ni(Ⅱ)离子是两步放电,其中吸附物Ni(OH)ads是通过第1步产生。通过分析阻抗谱,除了在高频端出现一个容抗弧,在低频端出现的感抗弧,是由于 Ni(OH)ads在阴极驰豫过程引起的结果。实验过程中观察到的电化学行为和结果能够通过提出的机理得到解释,中间化合物 Ni(OH)ads在电极表面消耗。通过定量分析和模拟,得到了镍沉积过程的阻抗参数。镀液中柠檬酸钠的加入,增加了电荷转移电阻,减小了双电层电容。     

Nickel electrodeposition from leaching solution containing ammonia and chloride

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Nickel Electroplating

NICKEL ELECTROPLATING has been practicallyused for decades.There is an unknown part in theplating,although this is easy to plate.Applications ofthe plating are described from the practical viewpoint.Purpose of Nickel Electroplating(1)Decorative,and corrosion resistanceNickel electroplating is deposited on iron,cupper,zinc and aluminum substrate etc.,and chromiumplating is usually deposited on nickel plating.Hexavalent chromium plating has an important effecton the corrosion resisitan…     

Studies on the Influence of Hexadecylamine on Chromate Phosphate Coating on Aluminium

The effect of hexadecylamine (HDA) on a Chromate phosphate coating on aluminium was studied using an optimized Chromate phosphate bath, The addition of HDA was found to decrease the coating weight, but to enhance the coating quality and corrosion resistance. The inhibitory effect of HDA helps in regulating the excessive attack on the metal and its ability to reduce Cr⁶⁺ to Cr³⁺ compensates the possible time delay for the initiation of coating deposition due to the inhibition.     

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.     

Copper electrodeposition from cuprous chloride solutions containing lead, zinc or iron ions

Cuprous chloride hydrochloric acid solutions were electrolysed in a two compartments cell without agitation for copper extraction. It is found that the current density affects the colour and the size of copper deposits. During electrodeposition of copper from cuprous solution in the presence of various concentrations of lead, zinc or iron ions at different current densities, it is observed that lead isIn all experiments, the current efficiency for the copper codeposited with copper by increasing current density.deposition reaction fluctuates between 88.50% and 95.50%。     

Process of pulse electrodeposition nanocrystalline chromium from trivalent chromium bath

Nanocrystalline chromium coating was prepared by pulse electrodeposition from trivalent chromium bath containing carboxylate-urea as complexing agent. The effects of electrodeposition parameters such as current density, bath temperature and solution concentration on the thickness and electrodeposition velocity of Cr deposited films were investigated. The crystallographic structures, morphology and chemical composition of Cr deposited films were analyzed by means of XRD, SEM and EDS. The results indicate that the deposited films with thickness up to 11.2 μm possess a smooth and clean appearance, and the grain size is less than 100 nm. The coating is pure chromium and the Cr deposit has face-centered cubic （fcc） structure and exhibits a （210） growth preference. Both the electrodeposition velocity and thickness exist maximum under different concentration complex agents, ureas, acetates, different temperatures and current densities. Compared with direct current electrodeposition, the thicker coating and finer grains can be obtained at lower temperature and current density by pulse electrodeposition. The electrodepostion velocity is about 0.24 μm/min, which is faster than that by direct current electrodeposition. In l mol/L H2SO4, 3.5% NaCl and 10% NaOH solution, corrosion potential of Cr pulse-deposited film is about 100 mV higher than that of direct current. Corrosion and passivation current densities are lower and the nanocrystalline exhibits better corrosion resistance.     

三价铬脉冲电沉积纳米晶Ni-Cr合金工艺

采用脉冲电沉积方法对三价铬电沉积Ni-Cr合金镀层工艺进行研究,确定并优化三价铬脉冲电沉积Ni-Cr合金的最佳镀液配方及工艺参数。研究镀液中各成分及工艺参数对三价铬脉冲电沉积Ni-Cr合金厚度及合金镀层中铬的影响,利用扫描电镜和电子能谱分析Ni-Cr合金镀层的形貌、微观结构和化学组成。结果表明,镀层厚度和Ni-Cr合金中铬含量在不同浓度的络合剂、稳定剂、乙酸钠及不同的电流密度、温度、pH值、占空比和脉冲频率下都存在极大值,且Ni-Cr合金厚度随合金中铬含量的增加而减少。当铬含量为24%时,镀层的厚度大于10μm,无裂纹,其晶粒为纳米球状晶粒。     

工艺因素对氨基磺酸盐镀铟阴极电流效率的影响

对氨基磺酸盐体系镀铟阴极电流效率的影响因素及其规律进行了系统的研究,通过分析镀液pH值、电流密度、镀液温度、添加剂以及电镀时间与阴极电流效率的关系,确定了镀铟最佳工艺参数.结果表明:当pH值为1.8～2.0,电流密度为1.8～2.2 A/dm2,温度为20～30 ℃,胺类添加剂加入量少于0.2g/L,电沉积1min,可以获得银白色的铟镀层,且阴极电流效率达到80%以上.     

工艺参数对电沉积纳米晶镍电流效率的影响

采用直流电沉积方法,通过改变特殊添加剂C7H4NO3SNa·2H2O浓度、沉积液温度、电流密度,制备出不同厚度的纳米晶镍覆层材料,利用高分辨透射电子显微镜(HRTEM)对沉积覆层材料的组织结构进行分析,从理论上推导了电流效率的计算公式,对不同工艺条件下电流效率的变化规律进行了研究.结果表明:电沉积纳米晶镍的电流效率可按ηMk=2.4403×105v/ik计算得出;电沉积纳米晶镍的电流效率随着添加剂C7H4NO3SNa·2H2O浓度的增加而下降;随着电流密度和温度的增加先增加后下降,在温度60℃左右时最大.     

Zn–Fe alloy electrodeposition from chloride bath: Influence of deposition parameters on coatings morphology and structure

In this study, the kinetics of Zn–Fe codeposition was investigated in chloride acidic solution using cyclic voltammetry. Anomalous codeposition is detected and this mechanism depends on the Zn(II)/Fe(II) concentration ratio in the electrolytic bath. Influence of deposition parameters on the morphology and structure of the coatings is discussed using characterization techniques and using the anodic linear sweep voltametry (ALSV). The ratio between Zn(II)/Fe(II) considerably influences the structure of the alloys. Dense, uniform, and single‐phased Zn–Fe coatings could be obtained.     

槽边循环电解法回收电镀废水中Ni的研究

对槽边循环电解法回收电镀废水中Ni进行了分阶段实验研究,包括小型试验、扩大试验以及系统扩大试验。试验结果表明,适合工业生产中使用的操作条件如下：Ni离子浓度可在0．5～2．5/L变化,电流密度40～80A／m^2,槽电压3—6V,pH=4．5～5．5;当Ni离子浓度保持在1．0～2．5g／L,若连续操作电流密度采用100～150A／^2,则电流效率仍大于40％;若从高浓度操作到低浓度,每次回收到0．5/L,电流密度应取40～80A／^2,操作10次后,可回收到使浓度小于0．1g／L,弃掉,则回收槽的回收率大于99％;由3类不同规模试验的对比中可以看出,在相同条件下,电流效率几乎相等。研究表明,采用槽边循环电解法回收电镀废水中的Ni是完全可行的,且可保证较高回收效率。     

电流密度对熔盐电镀铝晶粒形貌的影响

结合扫描电镜形貌观察和能谱分析研究了AlCl3-NaCl-KCl低温无机熔盐体系中电镀铝时电流密度对Q235钢基体上铝晶粒沉积形貌的影响,并从铝晶粒沉积过程中总的自由能变化的角度对其析出规律进行探讨。结果表明,在由80%AlCl3+10%NaCl+10%KCl所组成的熔盐中,当温度为150℃、电流密度为20.0～98.7 mA/cm2范围内电镀时,均可在Q235钢表面上获得完整、致密的铝镀层。电流密度的大小直接影响铝晶粒的形态和尺寸。电流密度低时,铝晶粒呈片状;电流密度高时,铝晶粒呈颗粒状,且随电流密度的增大,铝晶粒尺寸呈现减小趋势。结合热力学和动力学探讨了电流密度大小对电镀铝晶粒尺寸及形貌的影响。电流密度对铝晶粒形貌的影响与铝晶粒在Q235钢基体上沉积时形核及长大过程中的总自由能变化,特别是由电流密度大小所决定的铝晶核析出电化学能的大小有关。     

电流密度对超临界CO2流体镍电铸层表面性能和过程参数的影响

采用非离子表面活性剂,进行超临界CO2流体(SCF-CO2)电铸金属镍的研究,分析电流密度对CO2超临界流体镍电铸层微观组织、显微硬度、阴极电流效率、沉积速率、铸层厚度的影响。结果表明,随着阴极表面电流密度从3A/dm2逐渐增加至9A/dm2,体系电流效率快速下降,金属镍电铸层的显微硬度、沉积速率、铸层厚度不断增大。在压力为10MPa,温度为323K,电流密度为5A/dm2时,镍电铸层的显微硬度、铸层厚度、阴极电流效率、沉积速率分别为7.01GPa、30.5μm、94.51%、51.85mg/cm2·h,与传统电铸方法相比较,SCF-CO2电铸法制备的镍电铸层表面平整、微观组织致密。     

Corrosion behaviour of magnesium sacrificial anodes in tap water

The effects of applied current, testing time and microstructure on the electrochemical properties of magnesium‐based sacrificial anodes in potable water were evaluated. Galvanostatic tests, potentiodynamic polarisation and scanning electron microscopy (SEM) analyses were used to determine anode efficiency, corrosion rate and microstructures of the Mg‐anodes under study. The contribution of processes as mechanical material loss and hydrogen evolution on the current wastage was investigated. The effect of the different microstructures like those obtained by heat treatments to reduce the intermetallic phase was also tested.