Zincate mechanism on cast Al-Si alloy in non-cyanide multi-metal zincate solutions

Arrhenius formula was applied to calculate the apparent activation energy of zincate reaction. The standard electrode potential of all the metal coordinating ions and the order of galvanic couple of different metals in zincate solution were also calculated. Electrochemical behavior of zincate process was studied by Tafel polarization curves, E—t curves, and electrochemical impedance spectroscopy(EIS). The results show that the apparent activation energy of zincate reaction in non-cyanide multi-metal zincate solution is smaller than that in simple zincate solution, and precipitation sequence of all the metals in zincate solution is Cu, Ni, Fe and Zn. Relationship between the potential at 30 s before zincate and coverage was attained according to the change of potential of zincate. EIS shows that inductive reactance is produced during zincate.

Effect of non-cyanide zincation process parameters on the microstructure of the zincation layer on A356 alloys

The effects of non-cyanide zincation process parameters on the microstructure of the zincation layer on A356 alloy were investigated by scanning electronic microscope.With the increasing of zincation time,the zinc grain size and the number density increase gradually,and the zinc grains adhere each other.The zinc grain obtained in the double-dipping process is finer,compacter and more homogeneous than that obtained in the single-dipping process.With the increasing of the zincation temperature,the morphology of zinc grains changes from spherical shape to flake-like shape.However,higher zincation temperature results in the flaking off of the zincation layer from the matrix.The optimized zincation temperature is 20-30 ℃.The quality of the zincation layer obtained in a low concentration,non-cyanide and multi-element zincation solutions is much better than these obtained in conventional high concentration zincation solution,dilute zincation solutions or a dilute zincation solution containing nickel.In addition,the matrix alloy and the pre-treatment also have significant influence on the morphology of the zincation layer.

Performance tests of multi-metal zincate solutions with zinc sulfate and zinc oxide

Morphology of zinc alloy layer,from zincate solution with zinc sulfate and zinc oxide respectively,together with the consequent deposit was observed with SEM and back scattering electron image.EDS was applied to analyze the components of zinc alloy layer and the interface of high-Si aluminum alloy substrate-zinc alloy-deposit.Besides,the surface morphology of the zincated aluminum alloy after immersing in 3.5% NaCl solution for 7 d,is observed and the corrosion rate was calculate.Finally,tension test is conducted to quantify the adhesion between high-Si aluminum cast substrate and the deposit.The results show that,the zinc oxide contained zincating solution with sodium potassium tartrate and sodium citrate is a better one in multi-metal zincating solutions.The zinc alloy layer from this one gets stable performance,perfect adhesion with deposit,and good corrosion resistance.

Electrochemical tests on zincating solution with zinc sulfate and zinc oxide

In order to find out a multi-metal zincate solution to get good micromorphology and fine adhesion of coatings, sulfate zincate and zinc oxide zincate with different chelating agents combinations, of which there are 8 solutions are designed. CHI630 electrochemical test system is applied to measure the φ—t curves of zincate process and Tafle curves of zincated plates in 3.5% NaCl medium. The analyzed results show that when molar ratio of sodium hydroxide to zinc ions is constant, the better chelating agents combination for multi-metal zincation solution is the combination of sodium potassium tartrate and sodium citrate in zinc oxide solution, from which zinc alloy is high in potential and perfect in corrosion resistance. After the second zincate immersion for 60s, the immersion potential is -1.606V(vs SCE). The corrosion current density is 6.612, J_ corr/(A·cm -2); and the corrosion potential is -1.381, φ_ corr(I=0)/V.

杂质硅对锌酸钠溶液结晶过程的影响机理研究

研究了杂质硅对锌酸钠溶液结晶过程的影响规律,通过结晶物相和热力学研究了杂质硅对锌酸钠溶液结构的影响.通过分析锌酸钠溶液的分解行为,考察了杂质硅浓度、晶种和温度等参数对锌酸钠溶液结晶过程的影响规律.结果表明,存在一个临界硅浓度,当硅浓度高于临界硅浓度时,杂质硅抑制结晶过程的进行;当硅浓度低于临界硅浓度时,杂质硅促进结晶过程的进行.以氧化锌作为晶种时,35,50和60℃时临界硅浓度分别为0.20~0.40,0.054~0.20和0~0.054 g/L.以氢氧化锌作为晶种时,35℃时临界硅浓度为0.20~0.40 g/L.临界硅浓度随温度的升高而降低.硅浓度低时,物相为多面体形的ε-Zn(OH)_(2);硅浓度高时,物相为纳米棒和长方体形的γ-Zn(OH)_(2),提高温度可以抑制γ-Zn(OH)_(2)的生成.硅杂质的存在可能促使锌酸钠溶液的结构发生了重构,使锌酸钠溶液中锌元素以Zn(OH)+的形式存在,升高温度则可减弱杂质硅的影响.

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。

光亮剂在碱性镀锌液中的阴极行为

选定锌酸盐镀锌液为基础溶液，采用旋转圆盘电极研究了某种缩醛类光亮剂在不同转速下的阴极极化曲线和不同转速下空白镀液的阴极极化曲线，确定了空白碱性镀锌液在所研究的范围内得到的海绵状镀层并非扩散控制，并给出了锌的阴极放电历程。而光亮剂的加入有效地提高了镀液的阴极极化能力。并通过分析不同转速下的J～w^1/2曲线，确定了该光亮剂的阴极行为符合列维奇提出的旋转圆盘电极理论公式。

用双环己酮乙二酰二腙分光光度法测定浸锌液中的Cu^(2+)

基于铜与双环己酮乙二酰二腙(BCO)的显色反应,以柠檬酸铵为掩蔽剂,氯化铵-氨水为缓冲溶液,调节溶液pH值为8.6～10.0,使铜与BCO的蓝色生成物稳定保持在水相中,直接进行光度分析,据此建立了测定浸锌液中铜的分光光度分析法。测试结果显示:显色溶液在600 nm处有最大吸收峰,Cu2+测量的范围是0.02～4.00mg/L;Zn2+,Fe3+浓度为Cu2+浓度的5.0倍,Ni2+浓度为Cu2+浓度的12.5倍时,对Cu2+浓度测定的影响在允许误差范围内;Al3+对Cu2+的测定基本无影响。本方法快速、准确,可作为浸锌液中Cu2+的现场分析方法。

锌离子液体系高效催化合成环状碳酸酯

研究了离子液体助催化的各种无机盐催化剂体系用于二氧化碳和环氧化合物通过环加成反应制备环状碳酸酯 ,结果表明锌盐催化剂体系能够非常高效地催化该反应 ,最高得到了 5 472h- 1的催化转化频率 (TOF)和 10 0 %的选择性 ,催化剂使用六次以后没有发现催化活性和选择性的下降 ,并且该催化剂体系能够适用于各种结构的环氧化合物。

高维护性碱性电镀锌-镍合金工艺的研究

优选了碱性电镀锌-镍合金的配位剂,优化了工艺参数,并搭配合理的维护方法,得到了高维护性的碱性电镀锌-镍合金工艺。

铝合金化学镀镍工艺研究与应用

报道一种在铝合金元件上实施化学镀镍的工艺方法。该方法包括在改进的锌酸盐溶液中经二次浸锌处理后，以碱性化学镀镍作底层，然后进行酸性化学镀镍，能在铝合金（ Ｌ Ｙ１２ｃｚ 、 Ｌ Ｄ３１ 等） 表面获得光亮的、具有优异附着力和良好的防腐蚀性能及其综合物理、化学特性的化学镀镍（ Ｎｉ－ Ｐ） 层。

无氰浸锌液的研究

开发了一种新型无氰铝及铝合金浸锌液,该产品具有结合强度高、结晶细致、浸锌层均匀、覆盖度高、外观光亮等特点,可用于化学镀镍前的浸锌操作。通过扫描电子显微镜照片(SEM)对比了结晶及覆盖度等性能。

铝及其合金浸锌技术的发展及现状

浸锌是铝及其合金特殊前处理中较为常见的方式,在实际生产中占有重要地位。对浸锌前处理的碱蚀和出光的改进方法进行了总结。较为详细的阐述了铝及铝合金浸锌溶液从浓溶液到稀溶液,从单纯浸锌到多元合金浸锌,从有氰到无氰的发展过程。同时,对浸锌工艺的改良与发展及浸锌机理的研究进行了简要评述。

添加剂对碱性锌酸盐溶液锌电沉积的影响（英文）

采用扫描电镜表征添加剂对碱性锌酸盐溶液锌电沉积层表面和截面形貌的影响。运用循环伏安法和交流阻抗技术研究不同浓度添加剂在锌电沉积过程中的作用机理。研究结果表明,随着添加剂A浓度的增加,锌的形核过电位增大,对锌还原的抑制作用增强。这是由于添加剂A在阴极表面的吸附作用覆盖了阴极表面活性位点,并阻碍了阴极放电造成的。交流阻抗谱分析表明,在添加剂A存在的情况下,锌电沉积的控制步骤由扩散控制变为混合控制。添加剂B对锌的形核过电位值的影响较小,抑制效果不明显,但同时加入两种添加剂时,在电极表面的吸附作用更加显著,对锌电沉积的抑制作用最大,两者表现出明显的协同作用。

浸锌合金过程参数测定

利用扫描电子显微镜(SEM)对试片表面浸锌后质量优秀与低劣的锌合金层的微观形貌进行了比较,观察了不同浸锌时间及温度所对应的锌合金层的微观形貌,利用能谱仪(EDS)定量测定了锌合金层组成成分,利用X射线荧光能谱(XRF)定量测定了不同浸锌时间的锌合金层组成成分及膜厚。研究了锌合金层表面明度、电位、膜重随浸锌时间的变化,膜重随浸锌温度的变化及浸锌后的试片在3.5%NaCl溶液中塔菲尔极化曲线,定性测定了试片浸锌后镀层的结合力。结果表明:锌合金层质量的好坏直接关系到镀层与基体的结合力,在浸锌合金过程中适合的参数可以间接表征锌合金层的质量。

一种铝硅合金浸锌溶液用稳定剂的优选

利用CHI630电化学分析测试仪研究了在浸锌溶液中加入不同稳定剂及不同含量的最优稳定剂后试片在浸锌过程中的活化电位随浸锌时间的变化曲线和浸锌后的试片在3.5%NaCl溶液中的极化曲线.结果表明,稳定剂可以提高浸锌后试片的稳定电位,提高浸锌层在3.5%NaCl溶液中的耐蚀性.稳定剂A是较适宜的浸锌溶液中的稳定剂,其适宜的用量为0.05 g/L^0.1 g/L.利用SEM、EDS对浸锌层、化学镀Ni-P层的形貌和成分进行了分析,镀层结合力合格,并初步探讨了浸锌溶液中稳定剂的作用机理.

浸锌液中三价铁离子的分析

为测定浸锌液中Fe3+的浓度,建立了以水杨酸钠为显色剂的分光光度分析方法。研究了显色剂用量、pH值以及铜、镍、锌等离子对浸锌液中Fe3+测定的影响。结果表明,当浸锌液中的Cu2+浓度小于2.56g/L、Ni2+浓度小于22.3g/L时,对Fe3+测定的影响可以忽略,而Zn2+不干扰Fe3+的测定。该方法快速、准确,可以作为浸锌液中Fe3+的现场分析方法。

低铁锌铁合金电镀新工艺

研究了在碱性锌酸盐镀液中加入含铁补充剂后,得到镀层含铁量为0.4%～0.8%的锌铁合金电镀新工艺,讨论了影响镀层铁含量的各种因素,测试了镀层及镀液的性能。结果表明,锌铁合金镀层与锌镀层相比,更加光亮、细致,结晶致密,耐蚀性得到进一步提高。

碱性镀锌电解液成分的优选

分析了碱性锌酸盐镀锌电解液成分对镀层外观的影响,通过对锌酸盐镀锌电解液成分和工艺参数进行正交试验,优选出锌酸盐镀锌最优配方和最佳工艺参数。结果表明,该镀锌溶液具备优良的深镀能力和均镀能力,工艺范围宽,镀锌层光泽均匀一致。