金属表面无铬替代处理技术的研究进展

金属表面铬酸盐转化膜不仅具有优异的耐腐蚀性能,还具有自我修复功能,但是环保的需要使得铬酸盐钝化工艺将逐渐被各种无铬钝化无毒技术所替代。介绍了硅酸盐、钼酸盐、稀土复合转化膜、有机硅烷等各种无铬钝化工艺的优缺点和发展现状。并指出了今后金属表面处理无铬无毒钝化的方向。     

无铬复合钝化膜的微观组织结构及耐腐蚀性能

目的解决热镀锌钢板表面六价铬钝化工艺所产生的环境污染问题。方法以钼酸铵、纳米硅溶胶、单宁酸、硅烷偶联剂KH151和KH792为主要原料配制新型环保的无铬复合钝化液,在镀锌板表面制备钝化膜。采用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线光电子能谱仪(XPS)分析无铬复合钝化膜表面的微观形貌、元素组成和化学成分,用电化学工作站测试Mo元素对镀锌板耐蚀性的影响,使用中性盐雾实验研究不同皮模量时膜层的耐蚀性。结果无铬复合钝化膜中的Mo元素可以抑制微裂纹的产生和发展,阻挡腐蚀性介质向金属基体扩散,提高复合硅烷膜的电阻。复合钝化膜的电化学交流阻抗比硅烷钝化膜提高了1.6倍,与六价铬钝化膜接近,可以有效抑制腐蚀电化学反应的发生,降低反应速度,提高膜层的耐蚀性。皮膜量为892 mg/m2时,膜层的腐蚀面积为0,耐蚀性达到六价铬钝化膜水平;皮膜量为1252 mg/m2时,耐蚀性能优异。结论制备的无铬复合钝化膜结合了硅烷钝化膜和钼酸盐钝化膜两方面的优点,提高了膜层的致密性和结合性,膜层耐腐蚀性接近/达到了六价铬钝化的效果。     

文摘辑要

镀锌及锌基合金无铬钝化研究最新进展综述了国内外镀锌及锌合金无铬钝化的研究进展,着重介绍了几种无机、有机钝化工艺。展望了无铬钝化技术的发展趋势,同时指出硅酸盐钝化膜是完全无毒环保型保护膜,耐腐蚀性较高,且钝化成本较低。因此,硅酸盐钝化将成为替代铬酸盐钝化工艺的主要研究方向之一。     

热镀锌钢板钝化工艺对耐蚀性的影响

为提高热镀锌钢板的耐蚀性,对热镀锌钢板铬酸盐钝化工艺进行了研究.采用盐雾试验、钝化膜的微观形貌等手段分析了钝化液浓度及钝化工艺参数(钝化液温度、烘干时间、烘干温度等)对热镀锌钢板铬酸盐钝化膜耐蚀性的影响.结果表明,采用试验确定的钝化工艺处理得到的钝化膜耐蚀性明显提高,对实际生产具有较好的指导意义.     

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。     

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     

镀锌板表面钝化技术的应用现状及研究进展

概述了国内外目前对镀锌钢板表面钝化技术的研究,如无机类无铬钝化、有机类无铬钝化,提出未来有机/无机复合钝化膜是研究的方向。     

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.     

热浸镀锌层上丙烯酸树脂和钨酸盐复合钝化工艺研究

运用丙烯酸树脂与钨酸盐复合钝化,通过正交试验法对热镀锌层钝化工艺进行了优化。此外,采用单因素变量法、硫酸铜点滴试验、中性盐雾腐蚀试验以及电化学测试研究了工艺参数对钝化膜外观和耐蚀性的影响。结果表明:最佳钝化工艺:45 g/L丙烯酸树脂,25 g/L钨酸钠,8 g/L硫脲,15 g/L KF,10 m L/L H_2O_2,pH值为11,钝化40 s,钝化温度30℃。通过最优钝化工艺能获得表面平整、光亮的钝化膜。钝化膜中性盐雾试验出现白锈的时间可达72 h,明显优于未钝化镀锌层。     

取代铬酸盐钝化处理工艺的动向

六价铬对人体、特别是对皮肤会造成伤害而成为环境问题,现在铬酸钝化膜,特别是镀锌层的铬酸盐钝化膜在欧洲已经受到限制。本文对铬酸盐钝化膜的性能以及所进行的以三价铬盐或无铬盐取代铬盐钝化的开发状况加以解说。     

热镀锌板三价铬钝化剂的制备及其钝化膜耐蚀性能

目的制备钝化膜耐蚀性良好的热镀锌板三价铬钝化剂。方法以铬酸酐、酒石酸盐、无机混酸、纳米硅溶胶为原料,制备三价铬钝化剂。采用该钝化剂对热镀锌板进行钝化处理,通过中性盐雾试验、Tafel极化曲线和交流阻抗谱分析钝化膜的耐蚀性能,并表征钝化膜的表面形貌和元素组成。结果钝化镀锌板经120 h中性盐雾试验后,腐蚀面积仅为5%。与未钝化镀锌板相比,钝化试样的自腐蚀电位有所正移,自腐蚀电流密度降低了约2个数量级。钝化膜表面较为平整,有少量白色颗粒沉积,膜中主要含有C,O,Si,Cr,Zn等元素,且Cr主要以三价和六价存在,Zn以二价存在。结论该三价铬钝化剂可提高镀锌板的耐蚀性能,具有较好的工业使用推广价值。     

稀土铈盐、镧盐钝化镀锌钢板表面性能对比

运用正交试验分别对稀土铈盐和镧盐钝化进行试验,得出该两种稀土盐钝化镀锌钢板的最优参数和工艺条件。醋酸铅点滴试验、盐雾试验、失重试验和电化学交流阻抗谱(EIS)测定表明,镧盐转化膜的耐蚀性优于铈盐转化膜,接近常规铬酸盐转化膜。扫描电镜(SEM)表明,镧盐转化膜明显比铈盐转化膜成膜致密,对基体覆盖度更高,且膜层相对较厚。XRD分析显示,铈盐成膜物质主要是CeO2,镧盐主要是La2O3。漆膜划格试验表明,镧盐转化膜附着力优于铈盐转化膜,达到5B标准,再涂装性能可靠。     

镀锌钢板钛盐/硅烷复合膜的耐蚀性研究

研究了镀锌钢板上钛盐钝化膜、硅烷转化膜、钛盐/硅烷复合转化膜的表面形貌和化学成分,并对比了这3种转化膜与普通铬酸盐转化膜的电化学行为和耐盐雾腐蚀性能。结果表明:镀锌钢板钝化后,腐蚀电流密度降低,极化电阻及交流阻抗得到极大提高;钛盐/硅烷复合膜的耐蚀性已经接近普通铬酸盐钝化。SEM和EIS分析表明,硅烷膜是一层物理遮盖膜。     

A comparative study of molybdate/silane composite films on galvanized steel with different treatment processes

Two types of molybdate/silane composite films were obtained on the surface of hot-dip galvanized steel sheets by either directly immersing in a solution containing silane and molybdate as additive (single-step process), or firstly immersing in a molybdate solution, then in a silane solution (two-step process). The chemical compositions and microstructures of the films were examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and reflection absorption infrared spectroscopy (RAIR). The corrosion resistances were investigated by electrochemical measurements and neutral salt spray (NSS) test. The results showed that the molybdate/silane composite film formed in the single-step process had a similar double-layer structure as that obtained in the two-step process. The inner layer was composed mainly of the elements O, Mo, Zn, and P, similar to the single molybdate film; whereas the outer layer was composed mainly of the elements C, O and Si, similar to the single silane film. Compared with the single molybdate or silane film, the corrosion current of the composite films was reduced and the impedance of the films was increased. Accordingly, the corrosion resistance of the composite films was remarkably enhanced to a level which was comparable to or even surpassing that of the conventional chromate passivation film.     

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.     

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。     

镀锌(合金)钢板无/低铬钝化技术研究状况

 综述了国内外替代镀锌(合金)钢板铬酸盐钝化工艺的多种无/低铬钝化技术及当前研究状况.     

热镀锌板钝化膜黑斑缺陷分析及控制

通过使用金相显微镜和扫描电子显微镜对镀锌钢板出现的钝化膜表面黑斑缺陷进行微观分析,认为黑斑形成的原因主要为镀锌板生产过程中拉矫机挤干辊未能将带钢表面的水分挤干并完全烘干,在后续钝化处理时带钢局部残留的水分造成钝化膜被水稀释而产生漏涂点,在钢卷运输和仓储过程中,带钢表面的钝化膜漏涂点部位氧化而产生黑斑缺陷。通过严格控制挤干辊运行状况、提高热风烘干温度至110 ℃后,未再出现类似钝化膜黑斑缺陷。