【作者】 刘栋；

【导师】 刘常升；

【作者基本信息】 东北大学 ， 材料学， 2008， 硕士

【摘要】 热镀锌板被广泛应用于汽车和家电等行业,但在潮湿环境中镀锌层容易受到腐蚀,在表面会形成白色疏松的腐蚀产物,影响镀锌层的外观质量和腐蚀性。钝化处理能有效改善镀锌层表面的耐蚀性和涂装性,提高其表面质量,延长其使用寿命。但是传统的铬酸盐钝化处理对环境污染严重,对人体危害大。现阶段国内拥有自主知识产权且效果达到铬酸盐钝化水平的无铬钝化技术尚属空白,本文研究了以无毒、无污染的BTESPT硅烷为主要成分,以无机添加剂为辅助的有机、无机复合钝化体系,用来取代传统的铬酸盐钝化处理技术。本文确立了以BTESPT硅烷为主要成分的无铬钝化体系,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BTESPT硅烷钝化液配方和钝化工艺参数对于钝化膜性能的影响进行了研究,并通过两轮正交实验优化确定了钝化液的组分和钝化工艺参数：BTESPT,5vol.%;水,14 vol.%；乙酸,0.5vol.%；乙醇,80.5%；钝化液水解温度为35℃；钝化时间为5s；固化温度为120℃；固化时间为30min；钝化液水解时间为72h。又分别通过添加0.001mol/L的硝酸铈和0.02g/L的硅溶胶成功改进了此钝化体系,使之钝化性能可以超过铬酸盐钝化体系。研究中采用激光共聚焦显微镜、扫描电子显微镜、原子力显微镜对BTESPT硅烷钝化膜表面微观形貌进行了研究。在微观形貌分析中发现钝化膜表面均匀、完整、致密但存在一些微裂纹。在钝化液中加入硝酸铈和硅溶胶改性后,钝化膜微裂纹减少。研究中利用傅立叶红外反射光谱FTIR分析了硅烷钝化膜的结构,结果表明膜中含有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BTESPT硅烷钝化膜的元素组成及存在形式。结果表明,钝化膜主要含有Zn、Si、O、S、C等元素。经Ar+溅射深度和成膜元素的窄幅扫描结果显示,钝化膜的最外层可能为SiOH、Si-O-Si、Si-O-C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、ZnSi03等化合物。并推断出该钝化膜的膜厚度约为200nm。研究中通过点滴实验、中性盐雾试验、浸泡实验等加速腐蚀实验证明BTESPT硅烷钝化可以显著改善热镀锌板的耐蚀性,但是由于钝化膜薄且没有自我修复能力,所以长期耐腐蚀性能和铬酸盐钝化膜相比还略有差距。添加0.001mol/L的硝酸铈或0.02g/L的硅溶胶改进后的钝化膜的耐蚀性能均有较大的提高,超过了铬酸盐钝化膜研究中运用Tafel极化曲线和EIS交流阻抗谱测试了钝化膜的腐蚀电化学性能。结果表明,经过BTESPT硅烷钝化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。热镀锌板经BTESPT硅烷钝化后的耐蚀性优于铬酸盐钝化,钝化工艺操作简单、稳定性好且无毒无污染,有望可以替代铬酸盐钝化技术。更多还原

【Abstract】 Hot dip galvanized steel plate has been widely used all over the world because of better anti-corrosion properties, but it is easy to erode to form white and loose products which can affect the appearance and corrosion resistance in moist environment. The treatment of passivation is an effective method to improve the performance of corrosion resistance and coating. Generally, as a very effective passivated agent, the chromate was used widely in the world for a long time. But the treatment of passivation can bring serious environmental pollution. Now, there isn’t any nontoxic passivated agent, which has self-own intellectual property rights, can replace the chromate passivation. In this article, the organic/inorganic composite passive system, which consists of nontoxic and non-contaminative silane(BTESPT) as the main ingredient and the inorganic additive as the accessorial ingredient, was prepared.The non-contaminative BTESPT passive system was researched in this thesis. The composition and technical parameters of the BTESPT passive solution was systematically studied by single factor experiments using the accelerated test methods of Lead acetate dropping test, neutral salt spray test and so all. The 2-round orthogonal test method were used to determinate the best composition and technical parameters of the BTESPT passive solution. The basic compositions of the BTESPT passive solution were as following:BTESPT,5vol.%; deionised water,14 vol.%; acetic acid,0.5 vol.%; ethanol,81.5vol.%. The technical parameters of the passivation were as following:passive solution temperature,35℃; passive solution hydrolysis time,72h; treatment time,5s; curing temperature,120℃; curing time, 30min. By adding 0.001 mol/L cerium nitrate and 0.02g/L Silica Sol, the non-contaminative BTESPT passive system was successfully improved, which made it better than contaminative passive system.The Electron Microscope, Atomic Force Microscope and Metallurgical Microscope were used to character the micromorphology on the surface of silane passive films. It was found that there were some microcracks on the surface of the BTESPT passive films. When adding additives such as cerium nitrate or silica sol to modify the BTESPT passive solution, the microcracks were further covered and suppressed, the passive films become more denser so that it reduced the eroding agents such as O2, H2O and Cl- to enter the surface of the zinc. The electrochemical corrosion of the zinc was controlled to improve the corrosion resistance.The characterization of the passive films was performed by Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS).The test results showed that passive films consist mainly of such organic functional groups as SiOH, Si-O-Si, Si-O-Zn, CH2,-SiO-. The XPS analysis gave information of the chemical composition of the passive films. The XPS testing results showed that consist mainly of such elements as C,O, Si, S, Zn. Sputtering depth and narrow scanning results showed that the outer layers were SiOH、Si-O-Si、Si-O-C. The inner layers were Si-O-Si, Si-O-Zn, etc. The interface layers might consists of ZnO、ZnS、ZnSiO3. Moreover, it was inferred the thickness of passive films is about 200nm.The corrosion performance of the passive films was evaluated by accelerated test methods of Lead acetate dropping test, neutral salt spray test. The silane film could give efficient protect to the HDG, but it was not as better as the contaminative film as the film did not have the self-healing ability. The film improved by 0.001 mol/L cerium nitrate or 0.02g/L Silica Sol acted better.The corrosion performance of the passive films was evaluated by Tafel polarization cure and electrochemical impedance spectroscopy (EIS). The results were shown that the self-corrosion potential obviously shifted to positive direction, corrosion polarization was controlled by anode process, self-corrosion tendency is significantly reduced. The EIS spectrums of the passive films were composed of two capacitive loops in first quadrant. The beeline that slope is one does not appear in the low frequency district. The corrosive system was controlled by the electrochemical corrosion control system.The corrosion resistance of BTESPT passivating treatment is better than that of chromate treatment, and its technical parameters are simple, the stability of passive solution is good. Therefore, it is the most promising alternative technologies of chromate treatment.更多还原