共查询到20条相似文献,搜索用时 62 毫秒
1.
《Electrochimica acta》1986,31(3):299-306
A study has been made of the pulse plating of chromium from the standard aqueous chromic acid baths containing sulfate catalyst in the regime of pulse periods from 0.1 ms to 1.0 s and duty cycles from 10 to 100%. The coulombic efficiences of the chromium deposition and hydrogen evolution reactions at the cathode and of the oxygen evolution at a lead anode were measured with a gravimetric and gas-volumetric analysis. The results indicate that pulse current (pc) reduced the coulombic efficiency of the cathodic chromium deposition reaction. Pulse current modified the morphology of chromium deposits. With pc the chromium deposits from the dilute chromic acid bath at 22°C were of a needle-like structure as compared to the hemispherical growth in dc plating. A flake-type chromium deposit was obtained with pc from the concentrated chromic acid bath at 65°C. Pulse current increased the grain sizes of chromium deposits. For the hydrogen and oxygen evolution reactions, pc behaved as a depolarizer and considerably increased the coulombic efficiencies of both reactions. 相似文献
2.
3.
以某型发动机的水泵轴为基体,在同一镀液和镀槽中电沉积制备乳白/光亮双层铬镀层。工艺流程为:前处理─装挂─入槽─镀乳白耐蚀铬─镀光亮耐磨铬─出槽─清洗─除氢─抛光─检验。镀液组成为:CrO3200~250g/L,H2SO42.2~2.6g/L,Cr3+离子2.0~3.5g/L。先在60~65℃、15~25A/dm2下施镀30min得到乳白铬镀层,随后在55~60℃、40~50A/dm2下施镀90min,即得乳白/光亮双层铬镀层。双层铬镀层的孔隙率比单层光亮铬镀层小,二者显微硬度相近,耐磨性优越。实际生产应用表明,双层铬镀层的耐蚀性优于单层光亮铬镀层。 相似文献
4.
镀硬铬出现麻点的原因及对策 总被引:1,自引:0,他引:1
镀硬铬时出现麻点主要与基体表面局部产生点蚀有关。镀铬本身没有整平能力,点蚀处的电沉积层比平面部位少得多,故形成凹凸不平的镀层。其根源主要有工序间防锈不艮、酸洗时间过长、阳极电流密度过大和阳极刻蚀时间过长,退铬方法不当等:针对上述情况给出了预防措施.包括加强待镀工件的质检和工序间的防锈,控制酸洗除锈时间、阳极刻蚀时间和电流密度,采用适当的退铬方法等。 相似文献
5.
6.
某厂的气门在自动线镀硬铬时,杆部两端镀铬后尺寸偏小,尺寸小处经精磨杆部后光亮度不一,铬层明显未磨到,这大大影响了产品外观和质量。自动镀铬线的阴极屏蔽装置、阴极电流密度和温度、镀铬槽液、添加剂和开缸剂等都可能造成此次故障的发生,针对以上分析提出了相应解决的办法。 相似文献
7.
8.
以某表面处理公司的结晶器铜管镀硬铬脱脂废液为研究对象,先采用酸化法对废液中的配位铜离子进行破络处理,并通过调节pH使之沉淀析出,再采用Fenton试剂法降低废液的化学需氧量(COD)。研究了破络过程中FeSO4·7H2O的质量浓度和处理时间对破络效果的影响,以及降低COD过程中Fenton试剂的组成、处理时间和pH对废液COD的影响。脱脂废液处理的最佳工艺条件为:破络──FeSO4·7H2O12g/L,2h;降低COD──Fenton试剂为1.5g/LFeSO4·7H2O+4.5mL/LH2O2,pH=6.00,9h。在最佳工艺条件下处理过的脱脂废液澄清、透明,总铜含量满足GB21900-2008的排放要求,COD接近GB21900-2008的排放要求。 相似文献
9.
电镀液有许多技术性能指标,其中影响大的有阴极电流效率,以及镀液的分散能力与深镀能力.这三大指标是新工艺研究的必测指标. 相似文献
10.
L. Hallez M. De Petris-Wery M. Assoul M. Feki H. F. Ayedi 《Journal of Applied Electrochemistry》2007,37(7):843-852
In this work, a central composite design experiment was performed to estimate the effect of the electroplating parameters
(temperature of electrolyte, cathodic and anodic pulse current densities, and cathodic and anodic pulse lengths,) on four
properties of hard chromium electrodeposits. The studied responses were the hardness (Hv), the roughness quantified by the
two criteria Ra (nm) and R (μm)), and the specific abrasive energy, Es (μJ μm−3). Analysis of the responses using optimal path technique did not lead to a common set of experimental conditions which fulfilled
the required properties. Thus, the desirability function approach has been employed in order to find the best compromise between
the different experimental responses. The optimal conditions are: electrolyte temperature: 49.9 °C; cathodic pulse current
density: 42.0 A dm−2; anodic pulse current density: 51.5 A dm−2, cathodic pulse length: 6.23 s and anodic pulse length: 28.5 ms. Under these conditions, the estimated response values are
738 Hv, 262 nm, 2.61 μm and 0.027 μJ μm−3 for hardness, Ra, R and specific abrasive energy respectively, validated experimentally. The resultant coating, examined by AFM, exhibits
a nodular fine-grained morphology. 相似文献
11.
改进了六价铬镀铬溶液中三氧化铬和三价铬的分析方法。先用碘量法测定三氧化铬的浓度,然后在弱酸性条件下,不加硝酸银作催化剂,用过硫酸铵将三价铬氧化成六价铬,用碘量法测定六价铬的总量,减去镀液中初始六价铬的量,即得到三价铬的质量浓度。该方法与硝酸银催化强酸性氧化后硫酸亚铁铵滴定法的三价铬测定结果基本一致,精度符合实际生产要求,但操作更为简单,标准溶液更稳定,成本更低。 相似文献
12.
13.
14.
15.
16.
镀铬工业清洁生产的要求 总被引:5,自引:1,他引:4
根据清洁生产的要求,介绍镀铬减废技术,提出可用于铬酸回收、去除铬槽杂质、三价铬钝化、代铬等实用技术。认为电镀行业应加强对前处理、镀层匹配、挂具选择的重视。 相似文献
17.
18.
为提高圆筒状工件内壁电镀铬的沉积速度,采用自行研制的离心高速电镀铬装置。研究了电流密度与沉积速度、晶粒尺寸及镀层硬度的关系。结果表明,离心高速电镀铬的极限电流密度及沉积速度、镀层硬度均增大,镀层晶粒更细致。 相似文献