【作者】 单凤君；

【导师】 刘常升； 王林山；

【作者基本信息】 东北大学 ， 材料学， 2008， 博士

【摘要】 锌被大量用做钢的防腐蚀保护层。因为钢和锌层之间存在大的电位差,所以锌的溶解速率很高。在潮湿的环境中热镀锌钢板易发生腐蚀,使其表面形成白色的腐蚀产物或变成灰暗色,影响了热镀锌钢板的外观质量和镀层抗腐蚀性。为了降低锌在腐蚀性介质中的溶解速率,对热镀锌钢板广泛采用铬酸盐钝化的处理工艺。然而,六价铬酸盐属于极毒、致癌性物质、具有诱变作用。为满足环境友好型热镀锌表面处理钢板的需求,无铬热镀锌处理钢板的开发和生产逐渐得到重视,并取得了较快发展。本文研制开发以无毒、无污染的双-[γ-(三乙氧基硅)丙基]四硫化物硅烷(BTESPT)、γ-氨丙基三乙氧基硅烷(y-APS)为主要成分,以无机添加剂为辅助的有机/无机复合处理体系。通过单因素实验,利用醋酸铅点滴实验、中性盐雾实验等加速腐蚀试验手段对硅烷BTESPT处理液配方进行了设计和筛选,系统研究了硅烷BTESPT处理液的组成成分及用量,确定了硅烷BTESPT处理液的基本组成为：BTESPT5vol.%,水14vol.%,乙酸0.5vol.%,乙醇81vol.%,处理液水解温度为35℃。依据中性盐雾实验等级标准,运用对比实验方法对稀土硝酸盐、纳米级氧化物以及缓蚀剂等添加剂的种类、用量进行了研究,确定硅烷BTESPT处理液的改性添加剂及用量分别为硝酸铈O.OOlmol/L,硅溶胶0.005-0.02g/L,苯并三氮唑0.001g/L运用对比和正交实验方法对浸渍时间、处理液水解时间、固化时间及固化温度等工艺参数进行了确定,并研究了工艺参数变化对硅烷涂层性能的影响。结果表明,在工艺参数为：处理液水解时间72h,浸渍时间5s,固化温度120℃,固化时间30min时,硅烷BTESPT涂层具有良好的耐蚀性。运用Tafel极化曲线和EIS交流阻抗谱的腐蚀电化学方法测试了硅烷涂层的腐蚀性能。结果表明,经过BTESPT硅烷处理后的热镀锌试样的腐蚀极化过程是阳极控制型,自腐蚀电位明显的正移,自腐蚀倾向显著的降低；交流阻抗谱为第一象限两个半径较大的的容抗弧,在低频区未出现斜率为1的直线,腐蚀体系受电化学控制。利用傅立叶红外反射光谱FTIR分析了硅烷处理层的结构,结果表明硅烷处理层中含有SiOH、Si-O-Si、Si-O-Zn、CH2、-SiO-等主要有机官能团。利用XPS光电子能谱分析了硅烷BTESPT处理层的元素组成及存在形式。XPS分析结果表明,硅烷BTESPT处理层含有C、O、Si、S、Zn等元素。经Ar+射深度和成膜元素的窄幅扫描结果显示,硅烷BTESPT处理层的最外层可能为SiOH、Si-O-Si、Si-O-等结构,内层可能为Si-O-Si、Si-O-Zn等结构,界面层可能为ZnO、ZnS、ZnSiO3等化合物。硅烷BTESPT处理层的厚度约为200nm。采用电子显微镜、金相显微镜观察了硅烷BTESPT处理层的表面微观形貌。在微观形貌分析中发现硅烷BTESPT处理层的表面均匀、致密、完整、纳米结构,但存在一些微裂纹。通过加入稀土硝酸铈、硅溶胶、苯并三氮唑(BTA)添加剂改性硅烷BTESPT处理液后,弥补并减少了裂纹的进一步产生。由于铈的氧化物或氢氧化物、惰性硅酸盐膜等不溶性物质沉积或填充Si-O-S、Si-O-Zn的网络结构,使硅烷BTESPT涂层更致密,减少了外界O2、H2O、Cl-等腐蚀性物质接触金属锌的机会,抑制了锌的电化学腐蚀反应,因此大大提高了硅烷BTESPT涂层的抗蚀性。以1级中性盐雾实验标准为依据,通过对比实验确定了BTESPT/y-APS混合硅烷处理液的组成成分：硅烷BTESPT1-4vol.%,硅烷y-APS2-4vol.%,水量28vol.%,其余为乙醇,pH值4-6。由于硅烷γ-APS结构中含有-NH2亲水基团,促进硅烷BTESPT充分水解的同时,又能抑制硅醇的缩合,从而使耐蚀性显著提高。更多还原

【Abstract】 Zinc coating is a common material used in corrosion protection of steel. Due to great potential difference between the substrate and the zinc coating, zinc has high dissolution rate. In moist environment, the galvanized plate is easily corroded to form white products or become dark, which can affect the appearance of hot dip galvanized steel and decrease corrosion resistance. Chromate conversion coatings have been used widely to decrease the dissolution rate of zinc. However, the hexavalent chromium salts is a kind of extremely poisonous and carcinogenic material which has the mutafacient function. In order to make pretreatment technology satisfy environment-friendly demand, the chromate(VI)-free pretreatment for galvanized steel has increasingly developed. In this paper, the inorganic/organic compound treating system was prepared, in which nontoxic, nonpolluted bis-[triethoxysilylpropyl]tetrasulfide silane (BTESPT), gamma-aminopropyltriethoxysilane (y-APS) and inorganic additive is used as the main ingredient and the accessorial ingredient, respectively.The composition of the BTESPT treating solution was designed and sieved by single factor experiments using the accelerated test methods of lead acetate dropping test, neutral salt spray test and electrochemical corrosion test. The compositions of the treating solution were studied to determine the experimental parameters. The basic compositions of the BTESPT treating solution were as following: BTESPT 5vol.%, deionised water 14vol.%, acetic acid 0.5vol.%, ethanol 81vol%. The temperature for hydrolysis of the BTESPT treating solution is 35℃.On the basis of neutral salt spray test grading standards, the types and amounts of additives including rare earth nitrate, nano-oxides and corrosion inhibitors were studied using the contrastive experiment methods. The types and amounts of the selected additives of BTESPT treating solution were cerium nitrate 0.001mol/L, Silica Sol 0.005-0.02g/L, BTA 0.001g/L respectively.The parallel test method and orthogonal test method were used to determinate the dipping time, the hydrolysis time of the treating solution, the curing time and temperature of the BTESPT treating coating and the effects of experimental parameters on the properties of the treating coating. When the technical parameters change, BTESPT treating coating has a good corrosion resistance in the condition of the treating solution hydrolysis time 72h, dipping time 5s, curing temperature 120℃, curing time 30min.The corrosion performance of the BTESPT treating film was evaluated by Tafel polarization cure and electrochemical impedance spectroscopy(EIS). The results showed that the corrosion polarization was controlled by anode process, the self-corrosion potential obviously shifted toward positive direction, the self-corrosion tendency was significantly reduced. The EIS spectrums of the treating film were composed of two capacitive loops in first quadrant. The beeline with the slope is 1 didn’t appear in the low frequency domain. The corrosive system was controlled by the electrochemical control.The characterization of the silane treating film was analysed by Fourier transform infrared spectroscopy(FTIR). The test results showed that silane treating film consisted mainly of organic functional groups including SiOH, Si-O-Si, Si-O-Zn, CH2,-SiO-. The chemical compositions of the silane treating film were observed by X-ray photoelectron spectroscopy (XPS). The XPS testing results showed that treating film mainly consisted of the elements including C,O, Si, S, Zn. Sputtering depth and narrow scanning results showed that the outer layers of the BTESPT treating film composed of SiOH, Si-O-Si, Si-O-C, the inner layers composed of Si-O-Si, Si-O-Zn, etc, and the interface layers consisted of ZnO, ZnS, ZnSiO3. The thickness of BTESPT treating film was about 200 nm.The morphology of the BTESPT treating film was observed with Scanning Electron Microscope and Metallurgical Microscope. It was found the treating film was uniform, dense, integrity, nano-structure, but there were some microcracks on the surface of the treating film. When adding additives including cerium nitrate, silica sol and benzotriazole(BTA) to modify the BTESPT treating solution, the microcracks of treating film were further covered and decreased using the insoluble compounds such as cerium oxide or hydroxide, inert silicate to fill the network structure of Si-O-Si, Si-O-Zn, the treating film of Silane became more denser, reducing corrosive agents including O2,H2O and Cl-to enter the surface of the zinc and improving the corrosion resistance.According to 1 grade neutral salt spray test standards, the compositions of the mixed silane treating solution of BTESPT/γ-APS were determined by contrastive Test. The mixed silane treating solution consisted of BTESPT 1-4vol.%,γ-APS 2-4vol.%, deionized water 28vol.%, the rest is ethanol, pH value of 4 to 6. Becauseγ-APS structure contained-NH2 hydrophilic groups, BTESPT was more fully hydrolyzed, and condensation of silanol was inhibited, which significantly improved the corrosion resistance of the mixed silane films.更多还原