一种适用于强腐蚀环境下的无氰镀镉层结构

用新型氯化钾无氰镀镉工艺制备镀镉层,以低铬铬酸盐彩色钝化剂钝化,再用纳米羟基石墨烯改性封闭剂进行封闭。所制备的镀层按GB/T10125-1997《人造气氛腐蚀试验盐雾试验》进行中性盐雾试验,经过4000 h的喷雾测试,镀层表面无白色腐蚀物生成。这种镀层结构具有极高的耐蚀性,特别适用于海洋等强腐蚀环境下的防护性镀层。     

一种环保型锌合金无氰镀镉工艺

在锌合金基体表面上从内到外依次制备锌镍合金预镀层、无氰镀镉层、三价铬铬钝化层和纳米封闭层。锌镍合金预镀层采用碱性锌镍合金电镀工艺,或采用酸性锌镍合金电镀工艺制备。按照GB/T 10125-1997《人造气氛腐蚀试验盐雾试验》进行中性盐雾试验1728 h,镀件表面无白色腐蚀物生成;按照JB 2111-1977《金属覆盖层的结合强度试验方法》测定,镀层没有出现起泡和脱落。这种镀层结构具有优异的耐蚀性和良好的结合力,克服了采用氰化预镀铜和六价铬钝化存在高毒性的技术缺陷,具有较好的市场前景。     

表面催化系列

BZN-99新型碱性镀锌光亮剂 该剂系淡黄色或桔红色透明液体,具有很好的分散能力和深镀能力,镀层外观光亮细致,钝化膜耐蚀性好;镀液成分简单,工艺易维护等优点。适用于碱性无氰或低氰镀锌工艺。 工艺参数及规范: ZnO 8-12g/L(最佳值7.5g/L),温度5～45℃(最佳温度24℃),NaOH 100～120g/L(最佳值110g/L),阴阳面积比1:(1.5～2.5),BZN-99 6-8ml/L,Dk 1～4A/dm~2(挂镀) 0.2-1.0A/dm~2(滚镀)     

锌镍合金镀工艺优化及镀层耐腐蚀性的研究

目的研究锌镍合金镀层的耐腐蚀性能。方法通过正交试验法,对锌镍合金电镀工艺进行优化,获得镀液配方。通过中性盐雾试验评判优化后的锌镍合金镀层的耐腐蚀性能,并与镀锌层和镀镉层进行对比。分析主盐、络合剂、p H值、电流密度、温度等对镀层耐腐蚀性的影响。结果最优配方为:氧化锌6~14 g/L,硫酸镍20~30 g/L,氢氧化钠100~140 g/L,光亮剂4~6 g/L,络合剂50~70 g/L。该配方获得的锌镍合金镀层在中性盐雾实验中,出白锈的时间可以达到720 h以上。结论锌镍合金镀层的耐腐蚀性优良,优于镀锌层和镀镉层。     

镉镀层的大气腐蚀行为

采用常规氰化镀镉和无氰镀镉工艺在２０＃钢试样上镀敷镉镀层,并在青岛、江津、武汉和海南万宁大气试验站进行了５．８ａ的大气暴露试验．结果表明江津的镉镀层腐蚀速率最高,青岛与武汉的腐蚀速率接近,海南万宁的腐蚀速率最低．镉镀层不适用于有工业污染的大气环境,对海洋大气环境有较强的防护能力．无氰镀镉层的腐蚀速率与氰化镀镉接近,可以认为在一定条件下无氰镀镉能够代替氰化镀镉工艺用于上述４种典型的大气环境的腐蚀防护．     

光亮硫酸盐电镀Zn-Fe合金工艺研究

采用霍尔槽试验对硫酸盐镀锌铁合金光亮剂、辅助光亮剂、载体光亮剂进行了筛选,研究成功了一种酸性硫酸盐体系电镀低铁含量的光亮zn-Fe合金镀层工艺,探讨了主盐、络合剂、导电盐、稳定剂、工艺条件的影响,检测了镀液、镀层性能.结果表明:该镀液成分方便,镀液稳定,操作简单,所得镀层结晶细致、光亮平整,其耐蚀性与光亮度明显优于镀锌层,黑色钝化后黝黑发亮.     

铸铁表面化学镀Ni-P合金络合剂的研究

针对化学Ni-P镀过程中镀液稳定性差、使用寿命短、沉积速率低和pH范围窄等问题,采用对比实验和正交实验方法,以镀速、孔隙率、稳定性和镀层硬度为评价指标,研究了乳酸、苹果酸、柠檬酸和丁二酸络合剂及复合络合剂对镀液和镀层性能的影响.研究得到最优的铸铁表面Ni-P镀的复合络合剂配方为:乳酸20ml/L,苹果酸9g/L,丁二酸6g/L.此复合络合剂配方配制化学镀镍液可使镀速达到14.5μm/h,孔隙率降至0.45个/cm2,稳定性提高到3500s,硬度达620HV.     

低温酸性光亮化学镀镍

通过对络合剂、稳定剂、光亮剂的筛选 ,获得一种较理想的酸性化学镀镍工艺 ,该工艺具有沉积温度低 (70°C左右 )、镀速高 (8～ 1 0 μm/h)、镀层光亮、耐蚀性优异、镀液稳定性好、成本低等特点。     

氰化光亮镀镉生产实践

镉镀层和锌镀层作为钢铁的大气防护层得到较为广泛的应用.特别是在潮湿大气或海洋大气条件下,镉镀层的耐蚀性要比锌镀层高得多,并且镀镉钢的氢脆倾向比镀锌的要小,且对钢的疲劳性能影响也小.镉镀层较锌镀层软,尤其适用于螺纹紧固件.镉镀层还具有优良的钎焊性能和适宜的接触电阻,使镉的电沉积大量应用于多种产品,特别是在航空航天产品.本文就氰化光亮镀镉工艺生产实践做一简述.     

氧化锆陶瓷中温化学镀镍三元络合剂的研究

目的优化中温化学镀镍三元络合剂体系,得到性能优良的化学镀镍层。方法选取乳酸、冰乙酸及柠檬酸作为络合剂组分,以镀速和含磷量为考察指标,通过设计L9(34)正交实验,研究次亚磷酸钠、乳酸、冰乙酸及柠檬酸的浓度对化学镀镀速以及镀层磷含量的影响。结果综合考虑镀速和磷含量,得到的最佳三元络合剂体系为20 mL/L乳酸+15 mL/L冰乙酸+10 g/L柠檬酸,该条件下镀速为6.4 mg/h,镀层磷质量分数为8.8%。结论采用优化的络合剂体系,可以获得致密均匀、结合力良好的化学镀镍层。     

废弃物中回收镉的国内外现状探析

在查阅国内外文献资料的基础上,对从废弃物中回收镉的国内外现状进行了分析和探讨,指出对镉进行回收利用有很重要的现实意义,既能有效降低生产成本,充分利用资源,又能保护环境。     

从铜镉渣中回收镉的试验研究

本文介绍了从铜镉渣中回收镉的试验研究情况，采用酸浸-铜镉渣中和-锌粉除铜法处理铜镉渣，工艺简单合理，镉直收率高，有一定的推广价值。     

铝合金镀镉新工艺

从理论上对硬铝合金的浸锌工艺作了详细的论述。为使直升飞机机轮零件(硬铝材料)适应海洋气候,必须具有足够的抗盐雾性气氛腐蚀能力,锌酸盐浸工艺是提高抗腐蚀能力的较好方法,对硬铝合金的镀镉进行了试验并获得成功,投入了批量生产。     

N503萃淋树脂吸附镉的研究

研究了Ｎ５０３（Ｎ,Ｎ二仲辛基乙酰胺）萃淋树脂在氢溴酸、硫酸－溴化钠体系中对镉的吸附性能。探讨了Ｎ５０３萃淋树脂在氢溴酸体系中吸附镉的动力学和机理,发现Ｎ５０３萃淋树脂吸附镉的反应按拟一级反应进行,并符合Ｆｒｅｕｎｄｌｉｃｈ等温吸附式。由斜率法和饱和容量法确定Ｎ５０３萃淋树脂吸附镉的反应,镉以ＣｄＢｒ－３形式吸附在Ｎ５０３萃淋树脂上,镉与Ｎ５０３的摩尔比为１∶３。     

铅镉二元合金的共沉积添加剂

采用线性电位扫描法对铅、镉二元合金共沉积中适用的添加剂进行了筛选,研究了不同种类添加剂对铅、镉电沉积的影响,并分析讨论了添加剂的作用。通过对合金镀层中铅、镉元素含量的测定和合金镀层对应的阳极溶出极化曲线的测试和分析,证明了合金镀层中的铅、镉是一种单金属混合物。研究结果表明,采用本合金电沉积技术可获得镀层性能良好的、不同镉含量的铅、镉二元合金镀层。     

4340合金钢电刷镀镉工艺的应用

通过试验确定了4340合金钢电刷镀镉修复工艺的工艺流程及镀镉后钝化溶液的配方。镉镀层耐蚀性、氢含量以及结合力的检测结果表明,电刷镀镉是一种耐腐蚀、结合力良好、低氢脆的工艺方法,作为电镀镉层局部损伤后的修补镀层工艺,解决了钢类零件电镀镉层损伤后零件局部耐蚀性下降的难题。     

Biosorption of cadmium(Ⅱ) from aqueous solutions by industrial fungus Rhizopus cohnii

An important filamentous industrial fungus, Rhizopus cohnii (R. cohnii), was used as an efficient biosorbent for removing cadmium from wastewater. The sorption conditions, such as pH, the dose of biomass and the initial concentration of cadmium were examined. Two kinds of adsorption models were applied to simulate the biosorption data. The uptake of cadmium was higher in weak acid condition than in strong acid condition. Nearly no sorption of cadmium occurred when the pH value was lower than 2.0. Biosorption isothermal data could be well simulated by both Langmuir and Freundlich models. Langmuir simulation of the biosorption showed that the maximum uptake of cadmium was 40.5 mg/g (0.36 mmol/g) in the optimal conditions, which was higher than many other adsorbents, including biosorbents and activated carbon. In addition, the reusability results showed that after five times of sorption and desorption process, the sorption capacity of R. cohnii could still maintain nearly 80%, confirming its practical application in cadmium treatment. Fourier transform infrared spectrum revealed that carboxyl, amino and hydroxyl groups on biosorbent R. cohnii surface were responsible for the biosorption of cadmium.     

Selective separation of copper and cadmium from zinc solutions by low current density electrolysis

Copper and cadmium ions were selectively separated from zinc sulphate aqueous solution or zinc ammonia/ammonium sulphate aqueous solution by low current density electrolysis.It was shown that the concentration of cadmium ion in zinc sulphate solution decreased from 4.56 g/L to 0.18 g/L in an electrolysis time of 8.5 h,whilst it decreased from 5.16 g/L to lower than 0.005 g/L in zinc ammonia/ammonium sulphate aqueous solution.On the other hand,the deposition rate of copper was so low that it was difficult to...     

Effects of electroplated zinc-nickel alloy coatings on the fatigue strength of AISI 4340 high-strength steel

Recovered substrates have been extensively used in the aerospace field. Cadmium electroplating has been widely applied to promote protective coatings in aeronautical components, resulting in excellent corrosion protection combined with a good performance in cyclic loading. Ecological considerations allied to the increasing demands for corrosion resistance have resulted in the search for possible alternatives. Zinc-nickel (Zn-Ni) alloys have received considerable interest recently, because these coatings show advantages such as a good resistance to white and red rust, high plating rates, and acceptance in the market. In this study, the effect of electroplated Zn-Ni coatings on AISI 4340 high-strength steel was analyzed for rotating bending fatigue strength, corrosion, and adhesion resistance. The compressive residual stress field was measured by x-ray diffraction prior to fatigue tests. Optical microscopy documented coating thickness, adhesion characteristics, and coverage extent for nearly all substrates. Fractured fatigue specimens were investigated using scanning electron microscopy (SEM). Three different Zn-Ni coating thicknesses were tested, and comparisons with the rotating bending fatigue data from electroplated Cd specimens were performed. Experimental results differentiated the effects of the various coatings on the AISI 4340 steel behavior when submitted to fatigue testing and the influence of coating thickness on the fatigue strength.