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。     

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。     

压铸锌合金用三价铬钝化液的开发和应用

分析了一种高效、环保压铸锌合金用三价铬钝化液的主要成分及其操作工艺条件,优化了钝化液工作的参数,包括钝化液pH值、钝化温度和钝化时间的影响.研究结果表明,经三价铬钝化液处理后的锌合金,其钝化膜层均匀,色泽白亮、略显淡蓝色,耐中性盐雾腐蚀时间超过96h;该三价铬钝化液不仅有利于减轻原六价铬钝化液中六价铬对环境的污染,而且价格便宜、操作工艺简单.     

锌镀层钝化处理的研究现状及展望

介绍了锌镀层铬酸盐钝化和三价铬钝化的原理及应用前景;分别概述了高铬钝化、低铬彩色钝化、低铬蓝白钝化、军绿色钝化的优缺点;重点介绍低铬钝化和三价铬钝化的发展,并进行了展望.     

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。     

吉和昌推出系列三价铬蓝白钝化液

吉和昌化工自成立以来,即致力于表面处理化学品的研发、生产、销售及技术服务.在成功将水溶性氯化钾镀锌光亮剂808系列,碱性镀锌光亮剂628、629系列推向市场,并获得客户一致好评的基础之上,配套推出了一系列三价铬蓝白钝化液:Cr-B1N、Cr-B4N(硝酸铬体系)、Cr-B4S(硫酸铬体系)等,三价铬彩色钝化液Cr-C6N,高耐蚀无铬钝化液.     

钕铁硼三价铬彩色钝化工艺研究

开发了一种环保型三价铬彩色钝化工艺,通过实验研究了钝化液成分及钝化工艺对钝化膜耐腐蚀性能和外观的影响.结果显示:钕铁硼镀锌件通过三价铬彩色钝化可以获得致密的钝化膜,钝化膜具有优良的耐腐蚀性能,能够耐盐雾腐蚀96h.     

镀锌层三价铬钝化剂的探讨

适应保护环境的要求,研究了镀锌层三价铬钝化技术,在国内外一些典型的三价铬钝化配方基础上,试验研究发现,要获得良好钝化膜选用适当的络合剂是关键,并研制出能获得高耐蚀性钝化膜的三价铬蓝白钝化剂及彩色钝化剂,该钝化剂使用寿命长,镀液成份稳定,并得到了应用厂家的验证.     

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.     

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.     

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.     

锌酸盐镀锌层的三价铬溶液钝化

采用电化学方法、扫描电镜和X射线光电子能谱研究了锌酸盐镀锌层的三价铬钝化膜的电化学性能、表面结构与成膜机理。结果表明：锌酸盐镀锌层的三价铬钝化膜表面结构致密、无明显裂纹，具有较好的耐腐蚀性能；这种钝化膜表层与里层的组成不同，表层的组成为Cr2O3-Cr（OH）3-ZnO共混物；里层（离表层10-30nm处）的主要组成为Cr2O3-ZnO-Zn共混物；钝化膜的成膜过程可能包括镀锌层的溶解、碱性薄层的形成、胶状膜的形成和胶状膜转化成钝化膜4个步骤。     

硫酸铈对三价铬钝化膜耐腐蚀性的影响研究

目的研究硫酸铈对三价铬钝化膜耐蚀性能的影响。方法通过在三价铬镀铬盐溶液中分别添加0.3、0.5、0.8、1.0、1.5 g/L的硫酸铈,然后通过极化曲线测试,对比不同硫酸铈添加量的钝化膜的腐蚀电流密度,确定硫酸铈在三价铬镀铬盐溶液中的最佳添加量,然后分别制备未添加硫酸铈和添加最佳添加量硫酸铈的三价铬钝化膜,通过电化学工作站CHI660E测量Tafel极化曲线和电化学阻抗谱。分析钝化膜的电化学性能,研究不同钝化膜的耐腐蚀性。观察试样表面的微观形貌,对比添加硫酸铈和未添加硫酸铈的钝化膜的微观形貌。结果通过极化曲线测试发现,当硫酸铈的添加量为1.0 g/L时,钝化膜的腐蚀电流密度小于其余添加量的钝化膜,添加硫酸铈和未添加硫酸铈的钝化膜的耐蚀性能不同,添加硫酸铈后的钝化膜性能得到改善,且钝化膜膜层的微观形貌发生改变。结论添加硫酸铈后,三价铬钝化膜的耐腐蚀性能增强。当硫酸铈的添加量为1.0 g/L时,腐蚀电流密度最小,为3.835×10~(-6) A/cm~2,耐腐蚀性能优于其余钝化膜。     

Electroplating of wear-resistant nanocrystalline coatings from a bath containing basic chromium(III) sulfate (chrome tanning agent)

Regularities of the electroplating of chromium-carbon alloy coatings from a bath containing basic chromium(III) sulfate, carbamide, formic acid, sodium sulfate, aluminum sulfate, orthoboric acid, and sodium dodecyl sulfate are studied. Replacement of chromium sulfate as a source of trivalent chromium ions in the solution with basic chromium sulfate (chrome tanning agent) results in a decrease in the current density when metal deposition begins. As a result, the covering power of the bath increases. The effects discovered are determined by changes in the composition of the discharged chromium complexes. A certain excess of OH^? groups in the inner sphere of electroactive chromium complexes results in acceleration of electroplating. The studied electrolyte based on chrome tanning agent enables one to produce thick high-quality nanocrystalline Cr-C alloy coatings with improved tribological characteristics.     

铬铁矿中杂质铝和铁对铬氧化率的影响及其机理

以实验室合成的尖晶石型化合物为原料,系统地研究铬铁矿无钙焙烧体系中杂质铁和铝对Cr(Ⅲ)氧化率的影响规律及其机理。结果表明:铬铁矿中杂质铁对Cr(Ⅲ)的氧化率无明显影响;焙烧过程中FeO被氧化后得到的Fe2O3先与Na2CO3反应生成中间产物NaFeO2,它在体系中仍能起着Na2CO3的作用,使铬的氧化反应继续进行,整个Cr(Ⅲ)氧化过程的反应速率均较快;而杂质铝能明显抑制Cr(Ⅲ)的氧化,其主要原因是:在焙烧过程中,Al2O3与Cr2O3和MgO反应生成相对稳定、难溶的多元复杂氧化物MgO·(Cr2O3)0.5.(Al2O3)0.5。此外,Al2O3与Na2CO3反应生成Na2O·Al2O3,但Na2O·Al2O3很难进一步与MgO.(Cr2O3)0.5·(Al2O3)0.5反应生成Na2CrO4。     

A comparative study of the corrosion protective properties of chromium and chromium free passivation methods

Commercially available passivation methods for white-rust protection of hot-dip galvanized steel have been investigated. The passivations were either based on trivalent chromium or chromium free. A chromate based conversion coating was used for reference. The treated panels were tested with regard to white rust protection and paintability. The surface chemistry of the conversion coatings was monitored with scanning Auger electron spectroscopy and X-ray photoelectron spectroscopy. Coating thicknesses were measured using Auger electron sputter depth profiling.The passivations were applied with a thickness recommended by the supplier and thus showed large variation. The thickness of the chromium free passivation (Cr-free) is approximately 75 nm. The coating contains the active ions; H₃O⁺, Ti⁴⁺, Mn²⁺, Zn²⁺, PO₄³⁻. The passivation based on trivalent chromium (Cr-III) is approximately 30 nm thick and contains the active ions; H₃O⁺ Cr³⁺, PO₄³⁻, F. The chromate based passivation (Cr-VI) is approximately 5 nm thick and contains the active ions Cr⁶⁺/Cr³⁺, F⁻.The Cr-free and the Cr-III passivations showed similar white rust protection in the corrosion tests. The corrosion resistance was good although it did not fully reach the level of the Cr-VI passivation. The results from the tests of the painted panels showed that the powder paint worked well on all three passivations. The solvent born paint worked best on the passivation based on trivalent chromium. The water born paint showed poor resistance to blistering in the Cleveland humidity test for all three passivations. In this test the passivation with hexavalent chromium showed slightly better results than the chromate free passivations.