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三价铬硫酸盐溶液镀硬铬的辅助配位剂研究:前言

放大字体  缩小字体发布日期:2012-04-14  浏览次数:760

摘要:采用赫尔槽和方形槽电解试验,研究了三价铬硫酸盐溶液镀硬铬时乙酸、甘氨酸、柠檬酸钠、草酸钠、苹果酸等辅助配位剂对镀铬层外观、厚度和镀速的影响。结果表明,辅助配位剂有利于改善镀层质量扣得到光亮镀层,但平均镀速和镀层厚度明显减小。辅助配位剂的种类及添加量都会影响三价铬的电沉积过程。以O.4 mol/L甘氨酸作为辅助配位剂时,高电流密度区不漏镀,也不出现雾带,电流密度范围达到4.5~32.0A/din2,可得到整体光亮的合格镀层;以0.10 mol/L苹果酸作为辅助配位剂时,在电流密度为9 A/dm2的条件下持续电解20 min,可得到7.33 Bm厚的合格光亮镀层,镀速为21.96 wn/h。

关键词:三价铬;硫酸盐;镀硬铬;配位剂;厚度;镀速

中图分类号:TQl53.1 l    文献标志码:A

文章编号:1004—227X(2009)05—0005—05Effect  of  auxiliary  coordination  agent  in thedeposition  of  chromium  from  chromic  sulfateelectrolyte//WANG Qi。qiao.ZENG Zhen—OU*,K ANGZhen.hua。HU Yao.hongAbstract:The effects of auxiliary complexing agents,such as acetic acid,glycine,sodium citrate,sodium oxalate andmalic acid,on the appearance,thickness and electro.deposition rate of chromium coating from a chromic sulfateelectrolyte were studied using Hull cell and quadrate cell.Theresults showed that the addition of auxiliary complexingagent is helpful for improving the quality and brightness ofdeposit,but remarkably decreases the coating thickness andplating rate.The electrodeposition of仃ivalent chromiummay be affected by the type and dosage of auxiliarycomplexing agent.A wholly bright deposit was obtained byaddin9 0.4 mol/L glycine as auxiliary complexing agent atcurrent densities ranging from 4.5 A/dm2 t0 32.0 A/dm2.without showing foggy stripe and skip plating in high currentdensity area.A bright deposit having a thickness of 7.33 Ixmwas obtained by addin9 0.1 0 mol/L malic acid as auxiliarycomplexing agent at a current density of 9 A/dmz for 20 min,corresponding to a plating rate of21.96 IIm/h..Keywords:triValent chromium;sulfate;hard chromiumplating;complexing agent;thickness;deposition rateFirst-author’address:School of Chemistry&ChemicalEngineering,South China University of Technology,Guangzhou 5 10640,China

 

前言

 

    以三价铬溶液镀铬取代对环境污染较大的六价铬溶液镀铬,在装饰性镀铬方面已有工业应用[1-3],但在镀硬铬方面的进展缓慢,离实际应用还有较大差距。其主要原因是三价铬电沉积过程不能持续增厚。有学者认为[4-6],三价铬电沉积过程中大量析出的氢气使阴极表面附近溶液的pH迅速升高,当pH达到8.2时形成三价铬的氢氧化物沉淀,其覆盖在阴极表面或夹杂在镀铬层中,使阴极极化增大,阴极电流效率降低而导致铬镀层结晶的正常生长停止。也有学者认为[7-8]:三价铬的电沉积过程中,阴极表面附近溶液的pH/>4时,水合Cr(III)离子会发生羟桥化反应而抑制铬镀层结晶。因此,对于三价铬溶液体系镀硬铬而言,选择缓冲剂和添加一些具有缓冲作用的辅助配位剂尤为重要。三价铬硫酸盐溶液镀铬时,赫尔槽试验的试片在高电流密度区易出现漏镀和较深的雾带,导致可选择的电流密度范围窄;另外,电镀时间过长时,高电流密度区出现烧焦现象,从而影响镀铬层继续增厚[5,9-11]。为了解决三价铬硫酸盐溶液镀硬铬的连续增厚问题注:本站部分资料需要安装PDF阅读器才能查看,如果你不能浏览文章全文,请检查你是否已安装PDF阅读器!

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