碱性镀锌工艺

碱性镀锌工艺存在金属杂质影响大、镀液深镀能力差,镀层内应力大且三价铬钝化后容易产生花斑等缺陷,使得镀锌产品合格率低。以安特公司碱性镀锌为例,采用不锈钢镀镍板作不溶性阳极,增加溶锌槽,对镀液中光亮剂用量的调整等措施,使碱性镀锌工艺稳定,产品合格率提高。     

电镀用氧化锌的纯度及其杂质的分析方法

碱性锌酸盐镀锌所用的氧化锌,在溶液中是和氢氧化钠化合,形成络合物而存在的。由于氧化锌中含有异金属离子和其它杂质,特别是铜和铅对镀液带来很大的影响,如阴极电极电位增大、阳极大量析氧,同时发生阳极钝化,造成不溶性锌化合物增多,产生沉淀,镀液的深镀能力、覆盖能力、均镀能力变差,镀层发     

溶锌技术在无氰碱性镀锌中的应用

介绍了溶锌工艺的原理及在无氰碱性镀锌中的应用,设计制作了溶锌设备,并对镀槽中的碳素钢阳极加以改进,确保了镀液中锌离子浓度的稳定,保证了电镀质量。     

硫酸盐-柠檬酸盐体系锌锰合金电镀液稳定性的研究

锌锰合金镀液存在电流效率低,镀液稳定性差等缺点,选择硫酸盐－柠檬酸盐体系锌锰合金镀液,研究了阳极,二价锰离子以及连续作用等因素对镀液稳定性的影响,结果表明：采用不锈钢阳极和阴离子膜可提高镀液稳定性,防止二价被氧化,加入氢氧化可消除因补充锌锰离子而积累的硫酸根离子。     

碱性锌酸盐锌-铁合金电镀工艺

对德国科兹490锌-铁合金电镀工艺进行了全面介绍，包括工艺的特点、镀液的配制、镀液成分的作用、操作条件的影响、镀液的维护及其故障的排除。在镀槽中采用不溶性阳极可获得均匀的电流分布；采用辅助槽时，能得到综合性能最好的锌-铁合金镀层。     

氰化物镀锌转化为碱性锌酸盐镀液

1　前　言目前,氰化物镀锌将面临淘汰。氯化物镀锌和碱性锌酸盐镀锌是环保型电镀的方向。相比之下,碱性锌酸盐镀液分散能力和深镀能力好,适用于镀形状复杂的零件及锌合金压铸件,其镀层质量接近氰化物镀锌。碱性锌酸盐镀液与氰化物镀液相似,以氧化锌、氢氧化钠作为主要成分,选用     

不溶性阳极用于碱性镀锡的研究

探讨了不溶性阳极碱性镀锡镀液配方及操作条件,并且与采用可溶性锡阳极所获得的镀层进行了对比,测定了两种镀锡工艺的分散能力、阴极电流效率、覆盖能力和结合力,并且测试了所获得镀层的抗腐蚀能力。实验表明,两种工艺的镀液性能差别不大,但采用不溶性阳极进行碱性电镀锡更易于控制和维护。     

碱性锌-镍合金镀液及镀层中锌、镍的测定

酸性锌-镍合金镀液中锌、镍的测定方法报道很多，而碱性镀液中锌、镍的测定报道很少。采用过硫酸铵作氧化剂，在碱性介质中，镍与丁二酮肟生成红色络合物借此比色，求出镍含量；用EDTA滴定法确定锌、镍总量，然后减去镍量从中得到锌含量。此方法也可用于镀层中的锌及镍测定。本方法测定结果准确、快速，能满足实际生产的要求。     

碱性锌酸盐镀锌工艺管理

1前言碱性锌酸盐镀锌工艺因其成分简单、成本低、管理方便而在各类镀锌工艺中占有很大的比重。碱性锌酸盐镀锌工艺虽然简单，但如果管理不当，亦易经常发生质量事故，造成停产、返工、废品等现象；反之，则产品质量稳定，材料成本下降。笔者积多年镀锌工艺的管理经验，在本文中总结几个应注意的问题。2锌阳极要求纯度高的锌阳极。如果锌阳极不合格，会越镀越差，产生严重后果。鉴定锌阳极是否合格，应做金属杂质含量的化学分析。若无化验条件，在生产过程中要注意观察锌阳极的表面状态：正常的锌阳极表面溶解均匀，颜色一致呈银白色。而杂质…     

由锌杂质引起的氰化滚镀铜故障分析及处理

锌合金压铸件氰化滚镀铜液常受锌杂质污染,导致阳极钝化和镀层粗糙。分析了阳极钝化的化学反应过程,阐述了用氨水处理锌杂质的机理和方法。向镀液中加1mL/L25%的氨水,可促进锌和铜的共沉积,使锌杂质的浓度降低,2d后镀液恢复正常。氨水处理法简单,便于操作,不影响正常生产,明显优于硫化物沉淀法。     

Corrosion resistance of phosphate coatings obtained by cathodic electrochemical treatment: Role of anode–graphite versus steel

The formation of phosphate coatings by cathodic electrochemical treatment using graphite and steel anodes and evaluation of their corrosion resistance is addressed in this paper. The type of anode used, graphite/steel, has an obvious influence on the composition of the coating, resulting in zinc–zinc phosphate composite coating with graphite anode and zinc–iron alloy–zinc phosphate–zinc–iron phosphate composite coating with steel anode. The corrosion resistance of the coating is found to be a function of the composition of the coating. The deposition of zinc/zinc–iron alloy along with the zinc phosphate/zinc and zinc–iron phosphate using graphite/steel anodes has caused a cathodic shift in the E_corr compared to uncoated mild steel substrates. The i_corr values of these coatings is very high. EIS studies reveal that zinc/zinc–iron alloy dissolution is the predominant reaction during the initial stages of immersion. Subsequently, the formation of zinc and iron corrosion products imparts resistance to the charge transfer process and increases the corrosion resistance with increase in immersion time. The corrosion products formed might consist of oxides and hydroxychlorides of zinc and iron. The study suggests that cathodic electrochemical treatment could be effectively utilized to impart the desirable characteristics of the coating by choosing appropriate anode materials, bath composition and operating conditions.     

Copper anode corrosion affects power generation in microbial fuel cells

Non‐corrosive, carbon‐based materials are usually used as anodes in microbial fuel cells (MFCs). In some cases, however, metals have been used that can corrode (e.g. copper) or that are corrosion resistant (e.g. stainless steel, SS). Corrosion could increase current through galvanic (abiotic) current production or by increasing exposed surface area, or decrease current due to generation of toxic products from corrosion. In order to directly examine the effects of using corrodible metal anodes, MFCs with Cu were compared with reactors using SS and carbon cloth anodes. MFCs with Cu anodes initially showed high current generation similar to abiotic controls, but subsequently they produced little power (2 mW m^‐2). Higher power was produced with microbes using SS (12 mW m^‐2) or carbon cloth (880 mW m^‐2) anodes, with no power generated by abiotic controls. These results demonstrate that copper is an unsuitable anode material, due to corrosion and likely copper toxicity to microorganisms. © 2013 Society of Chemical Industry     

The production of oxalic acid from CO2 and H2O

Oxalic acid has been prepared on a preparative scale in an undivided cell with sacrificial anodes and an aprotic electrolyte. Optimum current efficiencies (>90%) have been obtained in cells with zinc anodes, stainless steel cathodes and acetonitrile with tetrabutylammonium perchlorate as the electrolyte. Micro-pilot experiments revealed that a continuous electrochemical cell can be set up and that the reaction product can be removed by filtration. A complete process is designed by a combination of the oxalic acid production with a zinc electrolysis. No unwanted by-products appear, which is recently of increasing importance. Economic consideration shows that the process may become interesting in the future.     

Comparison of the behaviour of glassy carbon and some metals for use as nonconsumable anodes in alumina-cryolite melts

Current interest exists in development of nonconsumable anodes for the Hall-Heroult process of aluminium production and also in situ analytical probes for determination of Al₂O₃ content in the cryolite melts used in this process. A comparison of the behaviour of glassy carbon and metals such as tungsten, tungsten carbide, nickel and stainless steel (SS-316) used as anodes in alumina-cryolite melts is investigated by means of electrochemical transient techniques (cyclic voltammetry and chronoamperometry) and Tafel anodic polarization experiments. The results show that only glassy carbon could be used as a successful sensor electrode for an in situ determination of Al₂0₃ in alumina-cryolite melts and that the metals investigated are unresistant to anodic attack in such melts. Consequently, the metals investigated cannot be used as sensor electrodes for in situ electro-analytical determination of alumina in alumina-cryolite melts, nor as anodes in the production of aluminium by the Hall-Heroult process.     

Anolyte cells of electrocoating paint. I: Anodes,impurities and dissolution

The occasionally occurring sudden destruction of the used stainless steel anodes during the electrocoating process and the regular consumption of their thickness are due respectively to local and non-local anodic dissolutions. The aim of this paper is to identify the operating conditions that protect the anode from the sudden destruction of local dissolution, and also to assess the non-local dissolution rate in order to predict the mean life of these anodes. Both types of dissolution are known in the field of corrosion, but this field concerns passivation and trans-passivation potential and not higher range, i.e. oxygen evolution reaction potential. Specific tests are performed with stainless steels that contain different concentrations of molybdenum and typical weak acids of anolyte solution that normally also contain traces of chloride, sulphate phosphate and nitrate as impurities. The results of these tests show that the anodes operate in non-safeguard conditions with respect local dissolution when: (i) traces of nitrates are absent from the anolyte solution and (ii) low molybdenum concentration stainless steels are used as anodes. When the safeguard conditions are ensured, the rate of non-local dissolution is easily detected and the results obtained show that its value increases with (i) the increase in molybdenum in the stainless steel, (ii) the decrease the pH value of the anolyte solution (iii) the increase in the temperature and (iv) the decrease in anolyte recycling in the cell. The results obtained show that sudden destruction and the mean life of anodes are the result of added chemicals in the paint bath and from the pre-treatments adopted. In other words, the interactions between pre-treatments, electrocoating and accessories (anodes), is required when the optimization of the electrocoating process is proposed.     

金属基有机硅树脂涂层复合材料的导热性能

以锌粉为导热填充剂对环氧有机硅树脂进行改性,考察了改性环氧有机硅树脂涂层干膜中锌粉含量对涂层导热系数的影响,分析了涂层厚度对碳钢基材导热性能的影响. 结果表明,环氧有机硅树脂涂层的导热系数约为0.19 W/(m?K),其耐温能力在200℃以上,可保证涂层在中低温烟气余热回收换热器表层长期工作而不发生任何热反应;添加锌粉可改善环氧改性有机硅涂层的导热性能,涂层干膜锌粉25wt%时,涂层材料导热系数达0.35 W/(m?K),较未添加锌粉时增大了84%. 复合材料的导热系数随涂层厚度增加而下降,无涂层的碳钢导热系数为47.59 W/(m?K),涂层厚度为200 ?m时,导热系数降至34.33 W/(m?K).     

新型炭阳极密度测量方法的开发与应用

针对成型预焙炭阳极密度测定方法中存在的问题，通过对国内厂家使用的密度测定方法的分析和研究，开发设计出了新型炭阳极密度测量装置，很好地解决了炭素行业中炭阳极密度测量的难题。     

Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries

The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about $15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about $1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization.     

Texture and surface morphology in zinc electrodeposits

The texture and morphology of zinc coatings electrodeposited on low carbon steel substrate have been studied. The predominant texture component of zinc coating at low overpotentials was pyramidal (11.5) and (11.6) non-fiber while at high overpotentials (00.2) fiber component dominated. The morphological analysis of the coating surface indicates that the non-fiber texture component results from epitaxial growth of zinc which develops through 2D nucleation and bunching growth of substrate surface microsteps, while the (00.2) fiber component starts from 3D nucleation and oriented growth to promote the plane having the lowest surface energy (i.e., (00.2)) parallel to the steel substrate surface. Zinc hydroxide adsorption prevents 3D nucleation at low overpotentials and this process favors epitaxial growth of the zinc deposit. At high overpotentials, inhibited zinc adsorption, in addition to increased number of active nucleation sites, promotes strong (00.2) fiber component. Such variation in texture indicates that the electrodeposit texture is strongly dependant on overpotential.