摘要
金属硅烷化处理是近年金属腐蚀防护领域中迅速发展起来的一种有望代替铬酸盐的绿色环保型处理技术。该技术基于硅烷分子水解后的硅羟基能和金属氧化物反应以及硅烷分子自身缩合形成无机/有机膜层的特点,以浸泡方式或电化学辅助沉积方式在金属表面制备具有疏水性能的膜层。这种膜层不仅能对金属基体提供保护作用,同时能够提高金属和涂层之间的附着力。
硅烷化处理技术经过人们不断研究和发展,至今已取得许多重要成果,部分技术已在工业中得到应用,如对镀锌钢的防腐。然而该技术仍不完善,现有技术制备的膜层存在薄、易水解、非均质等缺点,特别是对自腐蚀电位较低的金属防护能力差,如铝合金、镁合金,限制了该技术的应用。
本文针对当前铝合金、镁合金硅烷化处理技术的难点,在前人研究的基础上,分别在硅烷溶液添加辅助沉积剂和膜层改性剂,优化膜层制备条件,提高膜层的厚度、致密性,改善膜层的组成结构,增强膜层的抗腐蚀性能。实验结果如下: 1、本实验在低阴极沉积电位条件下,以表面活性剂改性硅烷溶液,实现了双-1,2-[3(三乙氧基)硅丙基]四硫化物BTSPS在铝合金电极表面的电化学沉积,新的临界沉积电位(NCCP)约为-1.6 V。交流阻抗EIS和极化曲线测试结果表明,在改性后的硅烷溶液中双-1,2-[3(三乙氧基)硅丙基]四硫化物在铝合金表面的低阴极电位沉积膜层具有较高的极化阻力。扫描电镜(SEM)结果显示在低阴极沉积电位下铝合金表面能得到更厚、更致密的硅烷膜层。硅烷溶液中表面活性剂的加入可以降低硅烷电沉积时的析氢影响,提高硅烷的沉积性能。较低临界沉积电位制备的硅烷覆盖铝合金电极比临界沉积电位(-0.8 V)下的硅烷覆盖铝合金电极具有更好的抗腐蚀性能。
2、在硅烷浸泡沉积的基础上,在溶液中加入添加剂B改善膜层的化学结构。交流阻抗EIS和极化曲线测量表明,在膜层中掺入添加剂B能有效提高膜层的极化电阻和孔隙电阻,增强膜层的抗腐蚀能力。衰减全反射-傅里叶变换红外光谱法FTIR– ATR测试显示,加入添加剂后,膜层的化学结构特征发生变化,证明添加剂已成功掺杂入硅烷膜层。实验中添加剂B的最佳加入浓度为9.7 %,该条件下制备的膜层对镁合金具有最好防护效果。
Silane technology have been rapidly developed in the field of corrosion control of metals as one of the“green”replacements for conventional chromating, recent years. This technology is based on the characteristic of silane which can be hydrolyzed to silanol which can interact with metal oxide, and have self-condensation.The films can be prepared by electrodeposition or dipping, which offers not only corrosion protection of metals but also stable adhesion to abroad range of paints.
In the foretime, many import research achievements in silane technology have been obtained and parts of them have been applied to corrosion protection of metals in industry, such as galvanized steel.However, Up to now the technology still have many issues for solving, for example: the films are too thin, easy hydrolysis, non-homogenization. The films can’t protect aluminum alloy and magnesium alloy, which can be corroded easily.
In the study, assistant deposition agents and modifying agent is added into silane solution, in order to optimize conditions of preparation, the thickness, the compactness, the structure of films and enhance corrosion protection of metals. The results are as follows:
1、Bis-1,2-[triethoxysilylpropyl]tetrasulfide (BTSPS) films have been successfully deposited at low cathodic potential in silane solution modified by surfactant, and a new critical cathodic potential (NCCP), -1.6 V has been found. Electrochemical impedance spectroscopy (EIS) tests and polarization curves indicated that BTSPS films prepared at low cathodic potentials in modified silane solution exhibited obviously higher corrosion resistances in comparison with silane films prepared by conventional electrodeposition method. The scanning electron microscopy (SEM) images indicated the surface morphology of silane films prepared at low cathodic potential were more compact and thicker than those prepared at conventional critical cathodic potential (-0.8V).Hydrogen evolution could be decreased as well as the electrodeposition of silane could be improved while adding the surfactant.
2、Modifying agent B is added into silane solution in order to modify the structure of films prepared by dipping. Electrochemical impedance spectroscopy (EIS) tests and polarization curves indicated that the polasization resistance and the pore resistance of the films is higher than that of the films prepared in pure silane solution. Fourier Transform Attenuated Total Reflection Infrared Spectroscopy(FTIR-ATR) show that chemical structures and characteristics of films modified by modifying agent B have occurred, which imply that the modifying agent B have been successfully doped into the films. In the experiment, 9.7 mass % the modifying agent is optimum, the corrosion protection of metals coated by the modified films is best.
引文
[1] Roland W A. Conversion processes for aluminum: How can chromium be substitute.Atb M B Etallurgie: Acta Technica Belgica, 1998, 38 (4):51 - 57
[2] 李新立.磷化(Ⅰ) – 基本原理及分类.材料保护,1994,27(2):38 - 39
[3] 代明江,陈鹤鸣.铝阳极氧化机理研究.广东有色金属学报,1996,1(6):51 - 55
[4] 郭瑞光,杨杰,康娟.铝合金表面钛酸盐化学转化膜研究.电镀与涂饰,2006,25(1): 43 - 48
[5] 杨宁,龙晋明.稀土钝化金属防腐蚀表面处理新技术.稀土,2002,23(2):55 - 62
[6] 王成,江峰,林海潮.LY12铝合金三价铈盐溶液中成膜工艺.中国有色金属学报,2001,11(2):181 - 185
[7] 郑辅养,马廷春.铝合金上锂盐转化膜的耐蚀性能.电镀与涂饰,1999,18(3):11 – 12
[8] 吕玲敏,杨异,栗万仲.镁合金表面电镀铝前处理工艺的研究.轻合金加工技术,2007,35(3):46 - 48
[9] 王雪明,李爱菊,李国丽等.硅烷偶联剂在防腐涂层金属预处理中的应用研究.材料科学与工程学报,2005,23(1):146 - 150
[10] 刘京,胡吉明,张鉴清等.金属表面硅烷化防护处理及其研究现状.中国腐蚀与防护学报,2006,26(1):59 - 64
[11] Arkles B.Tailoring Surfaces with Silanes.ChemTech,1977,7(12):766 - 778.
[12] Van Ooij,傅德生,傅原.硅烷偶联剂在金属上的应用.表面技术,1998,28(4):37 - 40
[13] Vignesh P,Danqing Zhu,Van Ooij.Nanoparticle-filled silane films as chromate replacements for aluminum alloys.Progess in Organic Coatings,2003,47(4):384 - 392.
[14] Van Ooij,Zhu D,Stacy M,et al.Corrosion Protection Properties of Organofunctio -nal Silanes-An Overview.Tsinghua Science And Technology,2005,10(3):639 - 664
[15] Van Ooij,Subramanian Vijay.Method of preventing corrosion of metals using silanes.US Pat.6261638,2001-7-17
[16] Ji-Ming Hu,Liang Liu,Jian-Qing Zhang,et al.Effects of electrodeposition poten -tial on the corrosion properties of bis-1,2-[triethoxysilyl]ethane films on aluminum alloy.Electrochimica Acta,2006,51(19):3944 - 3949
[17] Sundararajan G P,Van Ooij.Silane based pretreatments for automotive steels.Surf Eng, 2000,16(4):315 - 320
[18] Van Ooij W J,Zhu D.Electrochemical impedance spectroscopy of bis- [triethoxy-silylpropyl]tetrasulfide on Al 2024 - T3 substrates.Corrosion,2001,57(5):413 - 427
[19] Zhu D,Van Ooij.Enhanced corrosion resistance of AA 2024-T3 and hot-dip galvanized steel using a mixture of bis-[triethoxysilylpropyl]tetrasulfide and bis-[tri -methoxysilylpropyl]amine.Electrochim Acta,2004,49(7):1113 – 1125
[20] Subramanian V,Van Ooij.Effect of the Amine Functional Group on Corrosion Rate of Iron Coated with Films of Organofunctional Silanes.Corrosion- March,1998,54(3): 204 – 215
[21] Montemor M F,Cabral A M,Zheludkevich M L,et al.The corrosion resistance of hot dip galvanized steel pretreated with Bis-functional silanes modified with microsilica.Surf Coat Technol,2006,200(9):2875 - 2885
[22] Palanivel V,Huang Y,Van Ooij W J.Effects of addition of corrosion inhibitors to silane films on the performance of AA2024-T3 in a 0.5M NaCl solution.Prog Org Coat,2005,53(2):153 - 168
[23] Sheffer M,Groysman A,Starosvetsky D,et al.Anion embedded sol–gel films on Al for corrosion protection.Corros Sci,2004,46(12):2975 - 2985
[24] Pepe A,Aparicio M,Cer′e S,et al.Preparation and characterization of cerium doped silica sol–gel coatings on glass and aluminum substrates.J Non-Cryst Solids,2004,348(15):162 - 171
[25] Trabelsi W,Cecilio P,Ferreira M G S,et al.Electrochemical assessment of the self-healing properties of Ce-dopedsilane solutions for the pre-treatment of galvanised steel substrates.Progress in Organic Coatings,2005,54(4):276 - 284
[26] Aramaki K.XPS and EPMA studies on self-healing mechanism of a protective film composed of hydrated cerium(III) oxide and sodium Phosphate on zinc.Corrosion Science,2003,45(1):199 - 210
[27] Palanivel W M.Modified silane thin film as an alternative to chromates for corrosion protection of AA2024-T3 alloy:[dissertation].Knoxville:Univ.of Cincinnati,2003,23-26
[28] Woo H,Reucroft P J,Jacob R J.Electrodeposition of organofunctional silanes and its influence on structural adhesive bonding.J Adhes Sci Technol,1993,7(7):681 – 697
[29] Shacham R,Avnir D,Mandler D.Electrodeposition of methylated sol-gel films on conducting surfaces.Adv Mater,1999,11(5):384 – 388
[30] Sheffer M,Groysman A,Mandler D.Electrodeposition of sol - gel films on Al for corrosion protection.Corros Sci,2003,45(12):2893 – 2904
[31] Gandhi J S,Van Ooij W J.Improved corrosion protection of aluminum alloys by electrodeposited silanes.J Mater Eng Perform,2004,13 (4):475 – 480
[32] Ji-Ming Hu,Liang Liu,Jian-Qing Zhang,e tal.Electrodeposition of silane films on aluminum alloys for corrosion protection.Progress in Organic Coatings,2007,58(4): 265 – 271
[33] Van Ooij W J,Zhu D.Corrosion protection of metals by water-based silane mixtures of bis-[trimethoxysilylpropyl]amine and vinyltriacetoxysilane.Progress in Organic Coatings,2004,49(1):42-53
[34] Osborne J H,Joshua Du Y,Damron M.Inorganic/organic hybrid coatings for aircraft aluminum alloy substrates.Prog in Organic Coat,2001,41(4):226-232
[35] 徐溢,唐守渊,滕毅等.金属表面处理用硅烷试剂的水解与缩聚.重庆大学学报,2002,25(10):72 - 74
[36] Osterholtz F D,Pohl D R.Silanes and Other Coupling Agents.In:Mittal K L(ed). Utrecht VSP,1992,119-120
[37] Arkles B,Steinmetz J R,Zazyczny J,et al.The Stability of Alkoxysilanes in Aqueous Solution.Adhesion Sci.Technol,1992,6(1):193 – 206
[38] Franquet A,De Laet J,Schram T,et al.Determination of the thickness of thin silane films on aluminium by means of spectroscopic ellipsometr.Thin Solid Films,2001,348(1):37 - 45
[39] 崔晓莉 ,江志裕 .交流阻抗谱的表示及应用 .上海师范大学学报 (自然科学版),2001,30(4):53 - 61
[40] Zhu D,Van Ooij W J.Structural characterization of bis-[3-(triethoxysilyl)propyl] -tetrasulfide and bis-[trimethoxysilylpropyl]amine silanes by FTIR and EIS.Journal of Adhesion Science and Technology,2002,16(1):1235 - 1260
[41] Hirayama R,Haruyama S.Electrochemical Impedance for Degraded Coated Steel Having Pores.Corrosion,1991,47(12):952 - 958
[42] 陈晓红,张倩芝,张卫红等.多重衰减全反射-红外光谱法在复合材料表面分析中的应用.散射学报,2007,19(2):158 - 162
[43] 王喜贵,施和平.红外光谱多重衰减全反射法定性测定不透明材料上的涂层.内蒙古石油化工,2000,26(1):46 - 48
