铝合金三价铬钝化液的研制和应用

分析了铝合金三价铬钝化液的钝化机制,研究了复合盐钝化剂用量、钝化处理时间和温度对钝化膜质量的影响。结果表明,经铝合金三价铬钝化液钝化后的试样,其抗腐蚀性能优于铬酸钝化液,可在常温下进行处理,且处理时间较短,有利于减轻铬酸钝化液中六价铬离子对环境的影响。     

镀锌蓝白钝化工艺研究现状与进展

近年来,随着人们对工艺环保的关注程度逐渐增强,最初的六价铬酸盐蓝白钝化工艺已经逐渐被三价铬蓝白钝化工艺所取代,三价铬毒性较小,大约为六价铬的1/100,比六价铬更易于处理,且六价铬钝化层中就是以三价铬离子为骨架成膜的,所以三价铬钝化是替代六价铬钝化极好的选择.在此进程中,国内外科技工作者开发出一些无毒的、环保型的     

机械镀锌镀层钝化与耐蚀性能研究

    对机械镀锌层分别用三价铬、稀土和六价铬进行了钝化处理,利用盐雾试验和电化学测试对不同钝化膜的耐蚀性与电化学行为进行了比较研究.盐雾试验结果表明,稀土与三价铬钝化处理的效果均已超过传统的六价铬钝化,比六价铬钝化膜的耐蚀性提高了一倍以上;稀土钝化膜的耐蚀性最好,三价铬钝化膜的耐蚀性仅次于稀土钝化膜的.电化学测试表明,三价铬、稀土和六价铬钝化膜都能够不同程度地抑制腐蚀的阴极电极反应,抑制阴极反应程度最大的是稀土钝化膜,其次是三价铬钝化膜,最小的是六价铬钝化膜.三价铬与稀土钝化工艺的环保和良好的防腐效果使其具有良好的应用前景.     

无铬钝化与三价铬钝化的研究进展

六价铬钝化工艺,毒性大,严重污染环境,电镀行业研究并采用无毒或低毒的钝化工艺势在必行.目前无铬钝化和三价铬钝化已取得积极的进展,三价铬钝化已应用于生产,并获得良好的效果.无铬钝化作为环保工艺,是将来钝化工艺发展的新方向.结合近年来无铬钝化和三价铬钝化的发展,对无铬钝化、三价铬钝化及封闭处理等进行了较详细的阐述.     

镀锌层三价铬钝化工艺的研究

对热镀锌层上采用三价铬盐和三价铬盐加丙稀酸树脂两种钝化液钝化,探讨钝化液浓度、pH、钝化处理温度和时间对膜层耐腐蚀性能的影响。确定其钝化工艺,以取代六价铬盐钝化。试验结果表明,三价铬钝化液的最佳组分是将CrO3还原为三价铬,HNO3为氧化剂,硫酸和硼酸为添加剂。三价铬加丙烯酸树脂钝化液是以Cr2(SO4)3为主盐,次磷酸钠为络合剂,HNO3为氧化剂,硫酸和硼酸为添加剂,再加入与水的最佳体积比为1∶3的丙烯酸树脂为最佳组成。采用三价铬盐或三价铬加丙稀酸树脂钝化均可推迟镀锌层出现白锈的时间,三价铬加丙烯酸树脂钝化液效果更好。     

三价铬电镀铬现状及发展趋势

长期以来,电镀铬通常采用六价铬电镀液.近年来,由于六价铬对环境等方面带来污染影响,于是加紧了对三价铬电镀的研究.实际上提出用三价铬代替六价铬的研究已经有很长时间.用三价铬镀装饰铬与六价铬电镀相比,具有很多优异特性,但在实际应用中也存在一些问题,其可镀性受到一定限制.因此,用三价铬电镀功能性铬还没有被实际广泛应用.还介绍了三价铬电镀的机理及展望,并提出了有待深入研究的问题.     

高择优取向碱性锌酸盐镀锌层的耐蚀性

采用盐水浸泡试验,电化学测试和盐雾试验研究了碱性锌酸盐体系中获得的高择优取向镀锌层和随机取向镀锌层的耐蚀性能,对比了不同取向镀锌层三价铬和六价铬钝化膜的耐蚀性;采用盐雾试验对比了两种取向镀锌层和氰化镀锌层的耐蚀性。结果表明,高择优取向镀锌层的耐蚀性优于随机取向镀锌层;两种取向的镀锌层经三价铬钝化比六价铬钝化耐蚀性要好;经三价铬钝化处理后的高择优取向镀锌层耐盐雾时间可达720h。     

铝合金三价铬本色钝化实践

介绍了铝合金三价铬钝化工艺流程和重要工序,分析了钝化液成分及操作条件对钝化工艺的影响。采用三价铬钝化工艺可使铝合金表层的耐蚀性大大提高。     

镀锌层三价铬黑色钝化膜的耐蚀性能

制备了一种环保、不含六价铬的三价铬黑色钝化液,选择适当的封闭剂,研究其在镀锌层表面钝化后的耐腐蚀性能。通过醋酸铅点滴试验、塔菲尔极化曲线测试、电化学阻抗测试检测钝化膜的耐蚀性及采用扫描电子显微镜观察其表面形貌。结果表明:镀锌层表面经三价铬黑色钝化后再进行封闭处理,弥补了Cr3+钝化后无自愈能力的缺点,显著提高了镀锌层钝化膜的耐腐蚀性能,而且达到了Cr6+黑色钝化的外观效果。     

防止钝化膜中出现六价铬的措施

正0前言欧盟出台《关于报废电子电器设备指令》(WEEE)和《关于在电子电器设备中禁止使用某些有害物质指令》(Ro HS),要求成员国确保从2006年7月1日起,投放于市场的新电子和电器设备不含有铅、汞、镉、六价铬、聚溴二苯醚和聚溴联苯等6种有害物质[1]。我国自2007年3月1日起,禁止投放于市场电子和电器设备使用该6种有害物质[2]。目前市面上提供了多种三价铬钝化液产品,其耐蚀性和装饰性已达到或超过六价铬钝化液的钝化效果[3,4],但是经三价铬钝化液处理的零件,放置一段时间后,在     

高耐蚀性三价铬蓝白色钝化膜获得方法

镀锌层蓝白色钝化膜耐腐蚀性差是电镀行业一个长期得不到解决的难题,六价铬盐蓝白色钝化膜是如此,三价铬盐蓝白色钝化膜也是如此;这是由于蓝白色钝化膜层太薄的缘故.为此,在增加蓝白色钝化膜的厚度方面进行了努力,终于研制成功了一种能获得较厚、具有高耐蚀性钝化膜的WX-3TC三价铬蓝白色钝化剂及其钝化工艺,盐雾试验出现白锈的时间可达240h以上,从而解决了蓝白色钝化膜耐腐蚀性差的难题.     

Influence of alloying elements on the corrosion resistance of rolled zinc sheet

The influence of alloying elements on the corrosion behaviour of rolled zinc sheet in aqueous media has been investigated by means of electrochemical techniques. All the changes in corrosion behaviour seen in this study could be attributed to modification of the formation or the stability of the passivating oxide film on the zinc surface. A low concentration of copper (0.6 wt.%) inhibited the formation of the passivating film and reduced the stability of the film. Conversely, a low concentration of chromium (0.5 wt.%) accelerated the passivation process and raised the stability of the film. The passivation and corrosion behaviour shown by a commercially produced ternary alloy containing copper and titanium additions was almost the same as the behaviour shown by a model binary alloy containing only copper. All the results obtained in this study were consistent with the hypothesis that alloying elements alter the electron-conducting and/or ion-conducting properties of the passivating oxide film.     

The corrosion-protective traits of electroplated multilayer zinc-iron-chromium deposits

A novel kind of three-layer zinciron-cbromium electroplated coating was tested and proven to possess good corrosion protective characteristic as well as acceptable decorative properties. A citric-chloride bath containing Fe(III)-complexes is suggested for electrodeposition of iron intermediate layer on the zinc deposit surface. Due to the low acidity (pH 5) and medium operating temperature (20-30°C), the electrolyte involved has no a strong etching effect and can be used for direct iron deposition on zinc. A finish chromium layer is deposited from formate-sulfate trivalent bath. The zinc layer corrodes through the pores of Fe and Cr layers and protects the steel substrate against corrosion. The iron and chromium layers decelerate the corrosion rate of zinc. The finish chromium layer provides with good decorative properties, and the intermediate iron layer ensures adhesion of chromium to the zinc.     

Cu-Ni合金BTA复配体系钝化处理工艺研究

采用苯并三氮唑(BTA)复配钝化体系对B10 Cu-Ni合金进行钝化处理,以提高其在含硫化物环境介质中的耐腐蚀性能,并研究工艺参数对钝化膜耐蚀性的影响规律.利用动电位极化曲线和电化学阻抗谱研究钝化膜的耐腐蚀性能,采用X射线光电子能谱分析钝化膜的化学成分.实验结果表明,在BTA与磺基水杨酸组成的复配体系中形成的钝化膜比BTA单一体系中形成的钝化膜具有更高的耐蚀性,这是磺基水杨酸与基体合金反应形成的络合物膜与Cu(I)BTA膜协同作用的结果;钝化处理的时间和温度是影响钝化膜耐蚀性的重要工艺参数,延长钝化时间和提高钝化温度均可以提高钝化膜的耐蚀性,60℃高温条件下5 min的钝化处理即能够达到常温条件下3 h的钝化处理效果.     

Selective dissolution and surface enrichment of alloy components of passivated Fe18Cr and Fe18Cr3Mo single crystals

The possible surface enrichment of chromium and molybdenum during dissolution of Fe18Cr (110) and Fe18Cr3Mo (110) alloys at constant potentials in the passive region is elucidated by taking into account quantitative information on partial dissolution rates of alloy components as measured by γ-spectrometry and on chemical composition of passivating films as measured by ESCA and AES. Combining results from all methods it is found that chromium under all conditions is enriched in the passivating films. An accumulation of chromium in the alloy is also indicated. For molybdenum, an enrichment in the passive film is observed at ? 0.2 V (SCE), whereas in the potential interval 0.1–0.9 V, the molybdenum enrichment as determined by ESCA and AES is hardly significant. On the other hand, γ-spectrometry gives a clear indication of molybdenum enrichment in both potential regions.     

Untersuchungen zum Aktiv/Passiv-Übergang von nichtrostenden Chromnickelstählen in organisch wäßrigen Medien. Teil 3. Resultate der Impedanzmessungen und Passivierungsmodell einer Legierung

Investigations into the active/passive transition of 304 stainless steel in organic media containing water and hydrogen chloride Part 3. Results of the impedance measurements and passivation model of an alloy Steady state polarization curves and electrode impedances were measured during the active/passive transition of type 304 stainless steel in dearated ethanolic solution containing hydrogen chloride and different amounts of water. The passivation potential and the critical current density for passivation strongly depend on the water content of the solution. The impedance measurements in the active/passive transition show the same sequence of diagrams independent of the water content of the solution. They indicate the onset of passivation before the maximum current density and show two time constants related to two different passivating species on the alloy surface. The experimental results were interpreted on the basis of a reaction model with parallel dissolution and passivation mechanism of the iron and the chromium compound of the alloy. The resulting total surface composition (related to the steady-state polarization curves) can be described with a reaction model of iron–the alloy behaviour is that of pure metal. The fundamental passivation reaction is described as a potential dependent equilibrium between adsorbed Me(II)- and passivating Me(III)-hydroxide, water molecules being directly involved in the formation of this primary passivating film. In the case of stainless steel this primary passivating film mainly consists of chromium (III) adsorbates. Finally, a general model for the passivation is proposed: The passivation of a pure metal or of an alloy can be understood as the coupling of the stepwise deprotonation of the water molecules at the interface metal/solution and the formation of a high cation charge density in this adsorbed hydroxide/oxide film to build up the passive layer. The effect of water content, pH, adding of passivating species to the solution or the alloying with chromium on the passivation potential and the critical current density thus can be explained.     

三价铬电沉积铬基二元合金工艺的研究进展

近年来,由于六价铬的毒性及其对环境的严重危害,加快了三价铬电沉积的研究。但三价铬电沉积难以获得厚铬镀层,而铬基二元合金在镀厚性方面具有明显的优势。详细总结了三价铬体系电沉积铬镍、铬铁、铬钴、铬磷、铬碳和锌铬等二元合金的工艺,并简述了镀层的特性及应用。三价铬合金电镀将会在生产中有着广阔的应用前景。     

电沉积非晶态Cr—Fe—C合金镀层结构与性能研究

采用以三价铬为主盐的铬合金电镀工艺,对获得的Ｃｒ－Ｆｅ－Ｃ合金镀层的化学成分、结构、性能及其成因进行研究,结果表明,这种含铁量为２０％,含碳为５％左右的镀层为非晶态结构,含有大量微裂纹,微观上镀层表面呈结瘤状,热处理后可出现极明显的硬化现象,并伴随镀层逐渐向晶态转化。     

Managing the transition to hexavalent chromium free anti-corrosion coatings

Abstract

Hexavalent chromium is a well established material used in the commercial production of sacrificial zinc coatings for anti-corrosion applications. However, environmental and legislative pressures have been the catalyst for adopting alternatives based upon trivalent chromium and chromium-free materials. This change has wide implications within the global supply chain. End users and applicators must consider strategic issues such as product availability, cost implications and specific application needs. Experience with the change has illustrated the need for cooperation along the entire supply chain. The chemical supplier becomes the conduit between applicator and end user, and can facilitate a managed change of the process. Suppliers are ideally placed to establish best practice techniques at the applicator, and can work in partnership to achieve lowest operating cost with maximum performance. Developments in trivalent passivates for blue and iridescent colour films will be described, followed by discussion of the use of an audit approval programme to manage the transition to hexavalent chromium free products.