Mechanism of current efficiency improvement of Zn-Fe alloy electroplating by hydrogen inhibitor

The effect of hydrogen inhibitor on partial current densities ofZn, Fe and differential capacitance of electrode/electrolyte interface, and adsorbing type of hydrogen inhibitor were studied by the methods of electrochemistry. The mechanism of current efficiency improvement were explained from the point of valence electron theory. The results indicate that the partial current density of Fe increases in addition of hydrogen inhibitor, which reaches the maximum of 0.14 A/dm^2 when current density is 0.2 A/din〈 Differential capacitance of electrode/electrolyte interface decreases obviously from 20.3μF/cm^2 to 7 μF/cm^2 rapidly with the concentration varying from 0 to 20 mL/L, because hydrogen inhibitor chemically adsorbs on active points of Fe electrode surface selectively. Element S in hydrogen inhibitor with negative electricity and strong capacity of offering electron shares isolated electrons with Fe. The adsorption of H atom is inhibited when adsorbing on active points of Fe electrode surface firstly, and then current efficiency of Zn-Fe alloy electroplating is improved accordingly.

Surface pretreatment of Mg alloys prior to Al electroplating in TMPAC-AlCl_3 ionic liquids

It is difficult to directly electroplate Al on Mg alloys. The effects of pretreatment parameters on the corrosion resistance of films obtained on AZ31 Mg alloy surface were studied by using potentiodynamic polarization curves, to produce a compact interfacial layer as zinc-immersion deposition. After the substrate was pretreated under optimized conditions, aluminum was electrodeposited on AZ31 from TMPAC-AlCl3 room temperature ionic liquids. The depositions were characterized by scanning electron microscope equipped with energy dispersion X-ray. The results show that the traditional pretreatment of Mg alloys was successfully used for the Al-electroplating process from TMPAC-AlCl3 ionic liquids. The entire procedure includes alkaline cleaning, chemical pickling, surface activation （400 mL/L HF acid, 10 min）, zinc-immersion （20 min） and anhydrous treatment. A relatively compact zinc-immersion film was prepared on the substrate surface. A silvery-colored satin aluminum deposition was obtained on AZ31 from TMPAC-AlCl3 using direct current plating.

Progress of electroplating and electroless plating on magnesium alloy

The current research processes of electroplating and electroless Ni-P alloy plating on magnesium alloys were reviewed. Theoretically,the reason for difficulties in electroplating and electroless plating on magnesium alloys was given.The zinc immersion, copper immersion,direct electroless Ni-P alloy plating and electroplating and electroless plating on magnesium alloys prepared by chemical conversion coating were presented in detail.Especially,the research development of magnesium alloy AZ91 and AZ31 was discussed briefly.Based on the analysis,the existing problems and future research directions were then given.

Electroplating process of amorphous Fe-Ni-Cr alloy

A novel process of electroplating amorphous Fe Cr Ni alloy in chloride aqueous solution with Fe(Ⅱ), Ni(Ⅱ) and Cr(Ⅲ) was reported. Couple plasma atomic emission spectrometry (ICP AES), X ray diffractometry(XRD), scanning electronic microscopy(SEM), microhardness test and rapid heating cooling method were adopted to detect the properties of the amorphous Fe Ni Cr deposit, such as composition, crystalline structure, micrograph, hardness, and adherence between deposit and substrate. The effects of the operating parameters on the electrodeposit of the amorphous Fe Ni Cr alloy were discussed in detail. The results show that a 8.7?μm thick mirror like amorphous Fe Ni Cr alloy deposit, with Vicker’s hardness of 530 and composition of 45%～55% Fe, 33%～37% Ni, 9%～23% Cr was obtained by electroplating for 20?min at room temperature(10～30?℃), cathode current 10～16?A/dm 2, pH=1.0～3.0. The XRD patterns show that there only appears a broad hump around 2 θ of 41?°～47?°for the amorphous Fe Ni Cr alloy deposit, while the SEM micrographs show that the deposit contains only a few fine cracks but no pinholes.

Electroplating of Zr-Ti Alloy

The electrodeposition of Zr-Ti alloy has been studied in molten fluoride system consisting of fluorides of both zirconium and titanium dissolved in FLINAK (KF:NaF:LiF = 42.0:11.5:46.5 mol). A coherent dense deposit of the alloy with a smooth surface is obtained on different material substrates. X-ray diffraction has demonstrated that the alloy deposit is a Ti-Zr solid solution with Ti mainly and its preferred orientation is strongly along Ti[110] direction. The properties of the deposit are better than those of a pure zirconium coating. The optimum operating parameters are a temperature of about 800°C, a current density less than 40mA/cm2, a solution about 15wt% ZrF4 and 15wt% K2TiF6 in FLINAK as well as pure zirconium as anode material.

ELECTROPLATING OF AMORPHOUS Al-Mn ALLOYS(Ⅱ) KINETIC FEATURES OF ELECTRODEPOSITION OF Al-Mn ALLOYS

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Electroplating Zn-Al Alloy Technology

The method of controlling separating anode and separating power source was used to perform orthogonal optimization for the parameters in electroplating Zn Al alloy.The electroplating Zn-Al alloy technology was decided, in which the content of Al is about 12%-15% .

Electroplating zinc transition layer for electroless nickel plating on AM60 magnesium alloys

Electroplating zinc coating as transition layer of electroless nickel plating on AM60 magnesium alloys was investigated. The zinc film can be deposited in a pyrophosphate bath at 50-60℃under current density of 0.5-1.5 A/dm2. A new fore treatment technology was applied by acid cleaning with a solution containing molybdate and phosphorous acid, by alkaline cleaning in a bath containing molybdate and sodium hydroxide. The subsequent electroless plating was carried out in nickel sulfate bath. The SEM observation shows that the deposition is uniform and compact. The polarization curve measurements show that the corrosion potential of the zinc plating in 3.5% NaCl is about -1.3 V(vs SCE) which is noble than that of magnesium substrate. The zinc electroplating can be applied as the pretreatment process for electroless nickel plating on magnesium alloys.

Preparation of Amorphous Film on Ni-S Alloy by Electroplating Method

Beginning from the formation of amorphous alloy film and its use of proAnse, this paper obtains the Ni-S amorphous alloy film by electroplating method using a bath containing Na2S2O3, and considers the deposition conditions in detail. The composition of Ni-S alloy film changes with the cathodic current density, Na2S2O3 content in the bath solution and bath pH, but the structure of the film is detendned by the sulphur content in the deposit. X-ray diffraction (XRD) patterns show that films containing about 15-30% sulphur consist of amorphous alloy. In addition, the process of Ni-S alloy film deposition and the relation between the plating conditions and deposits were studied.

Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO_2 composite electrodeposition

Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO2 composite electrodeposition in alkaline zincatesolutions were studied respectively by the methods of linear potential sweep and cyclic voltammetry. From the re-sults it can be concluded that Zn shows under potential deposition, Zn-Fe alloy codeposition is anomalous codeposi-tion and Zn-Fe alloy cathode polarization is increased with the introduction of additive. From the view point of elec-trochemistry, the reasons that the content of Fe in the Zn-Fe coating changes with the composition of the electrolyteand the process conditions altering and the relationship between the content of Fe and the appearance of the coatingare interpreted. The cathode polarization of Zn-Fe alloy codeposition is enhanced obviously with addition of additive.In the course of composite electrodeposition, TiO2 has less promotion to electrodeposition of zinc ions than to iron i-ons, while the electrodeposition of iron ions improves the content of TiO2 in composite coating, which is inagreement with the results of process experiments.

THE PREPARATION AND APPLICATION OF ELECTROPLATEDSHEET CONTAINING RS ALUMINUM ALLOY POWDERS

Baded on the study of nickel electroplating technology at room temperature, the plated sheet containing rapidly solidified Al-Fe-Cu- V-Si-Ni-Ce-Zr aluminum alloy powders is constructed successfully. The powders and nickel matrix are combined well in the sheet. It can be used to prepare the observation specimen for TEM and determine the hardness of single powder particle as solidified and after heat-treated. The advantages of this method are the realization of heat treatment of powders and the TEM observation of non-interfered microstructure of powders in the size of several microns.

Electron beam braze-welding of vanadium alloy to stainless steel with electroplated Cu/Ag coatings

Cracks may easily occur in the fusion weld between vanadium alloys and stainless steel due to the brittle intermetallics and welding stress. The high vacuum electron beam braze-welding has been successfully used to join vanadium alloy（V-5Cr-STi） to stainless steel （HR-2） with electroplated Cu and Ag coating. To investigate the effects of electroplated coating on the weldability, the joint appearaace, the microstrueture and the mechanical properties of the joints have been thoroughly analyzed. The results show that the joint surface configuration was good and root reinforcement was full and smooth. A reaction zone （RZ） was gained on the interface between the V-5 Cr-5 Ti alloy and HR-2 stainless steel base metals. The width of reaction zone at the top of the joint was up to O. 65 mm, wider than that in the bottom of the joint （ 0.46 mm）. The reaction zone consisted of considerably smaller dendritic structures with an average grain size of less than 10μm. Element Ag and Cu almost enriched the interface between V-SCr-5Ti alloy substrate and RZ, serving as a physical barrier which decreases or avoids the formation of intermetallics. The maximum tensile strength of vanadium alloy^stainless steel dissimilar alloy joint was more than 300 MPa. The joint was defects free.

Current efficiency improvement of Zn-Fe alloy electrodeposition by hydrogen inhibitor

In order to inhibit hydrogen evolution and enhance current efficiency of Zn-Fe alloy electrodeposition from alkaline zincate solution, hydrogen inhibitors composed of the sulfur group elements were optimized on the basis of atom structures analysis. The effects of hydrogen inhibitor on the current efficiency of Zn-Fe alloy electroplating and their electrochemical behaviors were studied. The results indicate that hydrogen inhibitor can increase the current efficiency of Zn-Fe alloy electroplating evidently, from 63.28% without hydrogen inhibitor up to 83.54% with a hydrogen inhibitor at a volume fraction of 2.0%, while it has a minor influence on that of pure Zn plating, which maintains at 80%. The optimum volume fraction of hydrogen inhibitor is 2.0%.

Effect of Co-Deposited Iron on Microstructures and Properties of Electroplated Nanocrystalline Nickel-Iron Alloys

Nickel-iron nanocrystalline alloys with different compositions and grain sizes were fabricated by electroplating for MEMS devices. The iron content of the deposits was changed by varying the nickel/iron ion ratio in the electrolyte. X-ray diffraction (XRD) analysis was applied for measuring the strength of the texture and grain size of the deposits. The nickel/iron atom ratio of the deposits was analyzed by EDS. The hardness of the alloys was evaluated by Vickers hardness indenter. The internal stress of the deposits was measured by thin film stress measurement using Stoney's formula. Surface morphology and roughness were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Hardness and internal stress mechanism of the electroplated structure as a function of Fe ion content and current density were revealed. With increasing the iron content, the hardness and internal stress of the deposits increase. An excellent correlation between the increase in the internal stress and the loss of (200) texture were found.

Corrosion resistance of electroplated Zn-Co alloy coating

By the NSS test and the test in SO 2 gas atmosphere and detecting the  corr - t curves, R p- t curves and the cyclic voltammogram curves, the corrosion resistance of the electroplated Zn Co alloy coating was studied. The corrosion resistance of the electroplated Zn Co alloy coating is three times higher than that of the galvanized coating. Because the corrosion resistance of the Zn Co alloy coating is especially remarkable in SO 2 gas atmosphere, it is particularly fit to be used as a protective coating in industrial atmosphere. The reason why the Zn Co alloy coating has such a high corrosion resistance is that its corrosive product has a comparatively great role in depressing the corrosive process.

电镀Zn-Fe合金的发展现状

综述了Ｚｎ－Ｆｅ合金电镀的发展现状，阐述了Ｚｎ－Ｆｅ合金的电沉积机理、镀层结构及其抗蚀机理，指出了Ｚｎ－Ｆｅ合金电镀的发展方向。

碱性锌酸盐电镀Zn-Fe合金工艺的研究

研究了碱性锌酸盐电镀Zn Fe合金工艺 ,考察了合金镀液组成及工艺条件对合金镀层中铁含量的影响 ,得到了最佳镀液组成及工艺条件。实验发现 :Zn Fe合金的沉积表现为异常共沉积。在一定的范围内 ,镀层中铁含量升高 ,其光亮度随之提高 ;凡能影响镀层光亮度的条件发生变化 ,镀层中铁含量也随之变化。在最佳工艺条件下 ,可得到铁含量为 0 .2 %～ 0 .8%的兼具防护和装饰功能的Zn Fe合金镀层。

电镀Zn-Fe合金工艺研究

介绍了一种电镀Zn-Fe合金的工艺,研究了阴极电流密度、镀液中ρ(Fe2+)/ρ(Zn2+)、pH、温度和添加剂等因素对镀层的外观以及Fe质量分数的影响。实验结果表明,镀层中Fe的质量分数随着镀液中ρ(Fe2+)/ρ(Zn2+)、pH的增大而增大;随着阴极电流密度的增大、温度的升高先增大,达某一值时镀层中Fe的质量分数又随其增大而减小。通过3%NaC l腐蚀试验,比较了Zn-Fe合金和Zn镀层的耐腐蚀性。在最佳工艺条件下所得Zn-Fe合金镀层的耐腐蚀性为Zn镀层的5倍。

光亮硫酸盐电镀Zn-Fe合金工艺研究

采用霍尔槽试验对硫酸盐镀锌铁合金光亮剂、辅助光亮剂、载体光亮剂进行了筛选,研究成功了一种酸性硫酸盐体系电镀低铁含量的光亮Zn Fe合金镀层工艺,探讨了主盐、络合剂、导电盐、稳定剂、工艺条件的影响,检测了镀液、镀层性能。结果表明:该镀液成分方便,镀液稳定,操作简单,所得镀层结晶细致、光亮平整,其耐蚀性与光亮度明显优于镀锌层,黑色钝化后黝黑发亮。

Zn-Fe-P合金共沉积行为研究

采用H3PO3作为磷源制备Zn -Fe -P合金镀层 ,发现Zn -Fe-P合金镀层中Fe、P含量存在着同步效应 .采用循环伏安法研究了合金镀液中Fe2 + 和H3PO3的阴极电化学行为 ,发现镀液中的Fe2 + 和H3PO3彼此促进了对方的还原反应 ,并从量子化学的角度对镀层中Fe、P含量的这种同步效应进行了初步的理论探讨 .结果表明 ,由于铁的 4S轨道半径小于锌的 4S轨道半径 ,从而导致了铁的 4S空价轨道与磷的 3P空价轨道的重叠积分SFe -P大于锌的 4S空价轨道与磷的 3P空价轨道的重叠积分SZn -P,于是产生了镀层中Fe、P含量的同步效应 .研究还表明 ,铁族金属中Co、Ni与P的相互作用关系类似于Fe与P的相互作用关系 .