Induction centrifugal surfacing of the charge based on tin bronze powders with the addition of finely dispersed boehmite

The method of induction centrifugal surfacing of a charge based on tin bronze powders of medium dispersion with the addition of finely dispersed boehmite, which is an intermediate product in the production of the nanodispersed modification agent (α-Al₂O₃), is described. Its characteristic feature is that it can be produced in the surfacing conditions resulting in the chemical transformation of the intermediate product present in the charge to the nanodispersed modification agent followed by its uniform distribution in the liquid phase coating. The results of metallographic studies and tribotechnical tests of these coatings are presented. The experiments were carried out to determine the optimum (2–3%) boehmite content of the charge resulting in the highest parameters of antifriction and wear resistance properties of the coatings based on tin bronze after induction centrifugal surfacing.     

Tinplate and Tin Coating Technology

The application of tin as a coating dates back early into man’s metal-working history to when, for example, it was used as a decorative finish to bronze. The most likely reason for this initial application is tin’s low melting point coupled with its ability to wet and adhere to other metal surfaces. It was not until the industrial era that engineering uses for tin and tin-alloy coatings were arrived upon. While industry widely acknowledges the existence and application of tin coatings, not as many are aware of the field’s scope, which encompasses the complex technology of tinplate manufacture/use as well as an extraordinary variety of coatings that contain metals (apart from tin) and tin compounds. This paper reviews such current tin and tin-alloy applications as coatings, including tinplate, and describes related industrial developments and research.     

Electrodeposition of lead–tin alloy from methanesulphonate bath containing organic surfactants

The article discusses the process of electrodeposition of lead-tin alloy (tin content in the deposit up to 10–12 wt %) from methanesulfonate electrolytes. A composition was proposed of organic additives to the electrolyte providing attainment of high quality microcrystalline coatings with the alloy of predetermined composition at relatively low content of Sn²⁺ in the solution. It has been shown that the tin content in the deposit increases at an increase in current density and decrease in the electrolyte temperature. For production of anti-frictional Pb-Sn alloys with the tin content of about 10% the electrolysis should be performed at a current density of about 4 A/dm² and the temperature not exceeding 25°C. The effect of a decrease in the discharge rate of the Sn²⁺ ions into the alloy at deposition from electrolyte without organic additives was discovered, that is stipulated by deceleration of crystallization stage of tin on foreign substrate. When the alloy is deposited from electrolyte containing a composition of organic additives, the effect of super-polarization of discharge of Sn²⁺ ions is reduced.     

Corrosion and mechanical properties of epoxy-polyurethane/bronze composite coatings with low infrared emissivity

Low infrared emissivity coatings were prepared by using epoxy-polyurethane (EPU) and bronze as adhesives and fillers, respectively. Due to the increasing electrical conductivity with increasing bronze content, the infrared emissivity is decreasing obviously. Mechanical properties of EPU/bronze composite coatings were studied by using adhesion test and impact strength test. We found that EPU/bronze composite coating had good adherence and impact strength at bronze content below 50 wt.%, and then the mechanical properties decreased in the bronze content range from 50 wt.% to 60 wt.%. Moreover, the composite coatings were tested for the corrosion behavior with potentiodynamic polarization. Corrosion test results showed that the low emissivity EPU/bronze composite coatings exhibited favorable corrosion resistance. By comparing EPU/bronze, PU/Cu, (ball-milled Ag-Cu)/PU and PU/Al coatings, the EPU/bronze coatings with 40 wt.% bronze have the best adherence, low infrared emissivity and good corrosion resistance.     

Influence of electrodeposition parameters on the deposition rate and microhardness of nanocrystalline Ni coatings

In this paper, nanocrystalline nickel (nc-Ni) coatings were prepared by a direct current electrodeposition technique. Their microstructure and microhardness were investigated by a high-resolution transmission electron microscopy and a microhardness tester. It is found that the electrodeposition parameters, including content of C₇H₄NO₃SNa?2H₂O, temperature and current density, have significant influences on the electrodeposition rate and microhardness of nc-Ni coatings. The electrodeposition rate increases with the current density stepwise. The largest electrodeposition rate is achieved at 60 °C. It decrease when the temperature is larger than 60 °C. The electrodeposition rate decreases with the increased content of C₇H₄NO₃SNa?2H₂O. The microhardnesses of the nc-Ni coatings are higher on the condition of the larger current density, lower temperature or higher content of C₇H₄NO₃SNa?2H₂O. But, it remains stable when the current density is in the range of 700-1000 A m^− 2. The relationship between the mean grain sizes and microhardness fits for the Hall-Petch function, approximately.     

Electrodeposition of tin–nickel alloys from oxalate–sulfate and fluoride–chloride electrolytes

The processes of electrodeposition of tin–nickel alloys from sulfate–oxalate and fluoride–chloride electrolytes are investigated. Oxalate electrolytes for the deposition of the tin–nickel alloy have a high throwing power in comparison with that of the fluoride–chloride electrolyte. Increasing the polarization in the electrodeposition of alloys from an oxalate electrolyte provides an increase in the microhardness and corrosion resistance of coatings.     

Structure of a titanium-alloyed high-tin bronze obtained by the Osprey method

The titanium-alloyed bronzes with enhanced (14.5 and 15.5 wt %) tin content obtained by the Osprey method have been studied by the methods of optical, scanning, and transmission electron microscopy with the use of quantitative microanalysis in the initial state and after hot extrusion. These alloys have been employed as bronze matrices of multifilamentary superconducting Nb/Cu-Sn composites. An increase in the tin content in the bronze matrix makes it possible to enhance the critical current density of the multifilamentary composite owing to the improvement of the structure and composition of a superconducting Nb₃Sn compound that is formed upon diffusion annealing. It has been shown that the Osprey technology allows one to obtain bronzes with an enhanced Sn content and simultaneously to reduce the dendritic segregation characteristic of cast bronzes. The distribution of Sn and Ti in these alloys has been investigated. A more homogeneous structure in the initial state is characteristic of the alloy Cu-14.5Sn-0.24Ti (wt %). The increase in the tin content to 15.5 wt % leads to the formation of microregions of dendritic segregation with an (α + δ) eutectoid in the initial state, which slightly decreases plastic characteristics of this bronze.     

高速电喷镀纳米复合镀层组织与性能研究

采用高速电喷镀工艺制备纳米Ni／PTFE复合镀层。研究了电流密度、镀液中纳米PTFE含量等工艺参数对镀层性能的影响。研究结果表明，提高电流密度可显著提高复合镀层的沉积速率、镀层与基体的结合强度以及镀层的耐腐蚀性：镀层与基体的结合强度随镀液中PTFE的加入量的改变而变化，当加入量为10ml／L时，镀层经30次热震试验后，镀层无明显剥落：Ni与纳米PTFE共沉积可显著改善镀层的耐腐蚀性能。     

Antifriction coatings of Pb–Sn–Cu alloy electro-deposited from methanesulphonate bath

Abstract

Electrodeposition of antifriction Pb–Sn–Cu coatings from a bath based on methanesulphonic acid (MSA) has been investigated. The bath contains two specially selected organic additives which modify both the structure and the appearance of deposits, prevent the oxidisation of Sn(II) ions and allow the increase of tin content in deposits. The antifriction lead (～90%)–tin (～8%)–copper (～2%) films are deposited from the MSA-electrolyte at a current density of 4 A dm^?2 and a bath temperature of about 20–25°C. Inhibition of the Sn²⁺ ions discharge reaction is observed when the ternary alloy is deposited on the cathode. The Cu²⁺ ions discharge proceeds at a diffusion limiting current. Simultaneous co-deposition of copper has no effect on the kinetics of both lead and tin electrodeposition. Wear characteristics of the deposits from the methanesulphonate bath do not differ from those obtained from the usual fluoroborate bath.     

Electrodeposition behavior and characteristics of Ni-carbon nanotube composite coatings

Ni-CNT (carbon nanotube) composite coatings were processed by electrodeposition and their hardness and corrosion characteristics were investigated with variations of CNT concentration in an electrolyte solution and electrodeposition current density. With increasing the CNT concentration in the electrodeposition bath and the current density, more CNTs are incorporated into Ni matrix. Hardness values of the Ni-CNT coatings are irrelevant to the CNT concentration in the solution, the current density, and current mode, implying poor adhesion of CNTs to Ni matrix. With increasing the CNT content in the coating, the corrosion resistance of the Ni-CNT composite coating becomes inferior due to the porous microstructure.     

复合电铸CoNiMnP-BaFe12O19磁性复合材料工艺研究

磁性驱动器在微机电系统中有广泛的应用前景,获得电磁驱动的主要方法是在微驱动器表面电铸一层磁性镀层。该文采用复合电铸技术制备了CoNiMnP-BaFe12O19磁性纳米复合镀层,分别用SEM、EDS和VSM对复合镀层表面形貌、成分及电铸工艺参数（电流密度、搅拌强度、溶液温度及电铸时间）对复合镀层矫顽力Hc的影响进行分析。实验结果表明：BaFe12O19纳米颗粒的加入改变了Co、Ni、Mn和P在镀层中的含量,增大了镀层的表面粗糙度值,通过控制电铸参数可有效地调节镀层的矫顽力。     

Preparation and characterization of Cr-P coatings by electrodeposition from trivalent chromium electrolytes using malonic acid as complex

Cr-P coatings were prepared by electrodeposition from trivalent chromium plating bath using malonic acid as complex. The influences of bath composition on the trivalent chromium electrodeposition process and deposited coating properties were studied. The effects of plating parameters such as current density, bath pH and plating time on structure and morphology of deposited coatings were investigated in detail. XRD, SEM, EDAX and XPS techniques were used to characterize the Cr-P deposited coatings. Results show that the composition, microstructure and surface morphology of the Cr-P coatings depend on bath composition and plating conditions including bath pH, current density, plating time, etc. Results of EDAX and XPS indicate that the deposited coatings contain Cr(s), Cr(III), phosphorus, oxygen and carbon. The optimum bath composition was obtained using malonic acid as complex and the mechanism of Cr-P electrodeposition was analyzed. The optimum plating parameters for good-quality chromium deposited coating are pH 2-3, current density 3-12 dm², temperature 35 °C and Ti/IrO₂ as anode. These results may be of great practical and theoretical significance for further improvement of trivalent chromium plating process.     

工艺参数对Ni-纳米La2O3复合电沉积的影响

在氨基磺酸镍镀液中加入La2O3纳米颗粒,制备了Ni 纳米La2O3复合镀层.利用正交试验法研究了微粒悬浮量、电流密度、搅拌速度、温度等工艺参数对复合电沉积的影响,并用扫描电子显微镜对复合镀层的表面形貌进行了分析.结果表明,La2O3颗粒悬浮量对复合镀层La2O3共沉积量的影响最大;复合镀层中La2O3颗粒共沉积量越大、电流密度越小,其表面越平整、组织越致密.     

Improving the protective properties of La‐conversion coating on α‐brass surface by the combined use of La2O3 nanoparticles incorporation and electrodeposition

The La₂O₃ nanoparticles incorporation and electrodeposition were used together to prepare the La‐conversion coatings on α‐brass surface in a basal solution containing rare earth salt. The results showed that both techniques can improve the protective properties of coatings. A ‘critical nano‐La₂O₃ content’ and a ‘critical deposition potential’ were observed, under which the conversion coatings had the highest protective properties. Increased electrodeposition time improve the quality of conversion coatings. The La‐conversion coatings could provide important protection against α‐brass corrosion for considerable immersion periods in 3.5 wt% sodium chloride solution because it ennobled the corrosion potential and decreased the anodic current.     

电沉积方式对Ni-CeO_2纳米复合镀层摩擦磨损性能的影响

采用直流电沉积、脉冲电沉积和超声辅助脉冲电沉积制备Ni-CeO2纳米复合镀层,研究电沉积方式对纳米复合镀层表面形貌、显微硬度和摩擦磨损性能的影响,并用扫描电子显微镜分析其磨损机理。结果表明:电沉积方式对Ni-CeO2纳米复合镀层的晶粒尺寸和性能有较大影响;当超声波引入脉冲电沉积过程时,超声波的强力搅拌作用和超声空化效应能促进CeO2纳米颗粒在镀层中均匀分布,进一步减小镀层的晶粒尺寸,明显提高镀层的显微硬度,从而改善镀层的摩擦磨损性能;Ni-CeO2纳米复合镀层的摩擦磨损性能均优于纯Ni镀层的;而超声辅助脉冲电沉积制备的Ni-CeO2纳米复合镀层的晶粒更加细小、显微硬度最高,其摩擦因数最低,耐磨损性能最佳。     

工艺参数对电沉积制备铝镁合金的影响

目的以AlCl_3和LiAlH_4为溶质,苯和四氢呋喃为溶剂,进行电沉积铝镁合金,探索制备铝镁合金的最佳工艺条件。方法在AlCl_3-LiAlH_4-苯-四氢呋喃体系中,采用镁作阳极,通过预电沉积获得一定浓度的Mg~(2+),从而进行电沉积制备铝镁合金镀层。改变电流密度、沉积时间、预电沉积时间和预电沉积次数等参数,以探究工艺参数对铝镁镀层的形貌、晶粒大小和镁含量的影响,并通过SEM和EDS检测和分析铝镁合金的镀层形貌、成分及含量。结果镀层主要成分为Al_3Mg_2和Al_(12)Mg_(17),当电流密度为16.67 m A/cm~2时,获得的镀层表面效果最好,其晶粒尺寸可达1~2mm。预电沉积次数越多,通过预电沉积获得的Mg~(2+)越多,铝镁合金镀层中镁的含量越高,最高可达2.93%(质量分数)。结论在一定范围内,镀层中的镁含量随预电沉积时间的增加而提高。预电沉积次数越多,通过预电沉积溶解的Mg~(2+)越多,铝镁合金镀层中的镁含量越高。当沉积时间过长时,不利于镀层中镁含量的提高。铝镁镀层中的镁含量越高,电化学阻抗越大,腐蚀电位越大,镀层的耐腐蚀性能越好。     

Corrosion behaviour of bronze in urban environments: influence of tin content

Abstract

In this paper, the influence of the tin content on the corrosion behaviour of copper alloys was investigated. Three different bicomponent bronze alloys were exposed to a natural urban environment. The kinetic corrosion processes and the patina properties were monitored using the open circuit potential, electrochemical impedance spectroscopy and spectrocolorimetry. Results show that the bronze corrosion behaviour improves upon increasing the tin content. In addition, the mechanism of the patina formation is different for the three alloys.     

脉冲电沉积法制备高P镍基合金镀层

研究了脉冲参数(脉冲高度、宽度、以及反向脉冲等参数)对Ni-P合金镀层P含量、微观形貌等特性影响的规律。结果表明,平均电流密度与反向脉冲电流密度对镀层的P含量有较大地影响;占空比、频率对镀层的微观形貌影响较大。与直流电沉积法制备的Ni-P镀层相比,在不改变镀液组成的条件下,脉冲电沉积法可以显著提高Ni-P合金镀层的P含量。     

电沉积方式对 Ni-ZrO2 纳米复合镀层耐腐蚀性能的影响

目的改善Ni-ZrO2纳米复合镀层的耐腐蚀性能。方法分别采用普通电沉积、旋转阴极电沉积、超声电沉积和超声-旋转阴极电沉积四种方式制备Ni-ZrO2纳米复合镀层,分析镀层的ZrO2含量和微观形貌,研究镀层的耐腐蚀性能。结果普通电沉积镀层的ZrO2含量高,但晶粒粗大,组织不够致密,腐蚀速率高,腐蚀后的微观表面存在很多大的腐蚀坑洞。旋转阴极和超声辅助电沉积的镀层ZrO2含量较低,但晶粒有所细化,耐腐蚀性能提高。超声-旋转阴极电沉积的镀层ZrO2含量最低,但晶粒细化程度最高,组织致密度也最好,腐蚀速率低,表面腐蚀特征不明显。结论超声场和旋转阴极都会影响镀层的组织结构和ZrO2含量,超声波和旋转阴极协同作用下的效果最为显著,制备的纳米复合镀层耐腐蚀性能最好。     

含稀土镀液电沉积镍镀层耐蚀性的研究

借用扫描电镜、电化学分析和腐蚀失重实验方法研究了镀液中添加RE经直流和单向脉冲电沉积方法制备的镍镀层的耐蚀性。结果表明：单向脉冲法制备的镍镀层抗腐蚀能力优于直流法制备的镍镀层抗腐蚀能力，其原因主要归于单向脉冲镀层结晶比较细小致密，直流镀层结晶较粗大且致密性差。