【作者】 李林；

【导师】 姚素薇；

【作者基本信息】 天津大学 ， 应用化学， 2005， 硕士

【摘要】 涂料保护是防止金属腐蚀最重要最经济的手段。防腐涂料虽然品种繁多,功能各异,但防护效果还不很理想,主要是由于化学与力学失效引起的覆盖层寿命问题。因此,研制具有高防腐性能的涂料具有十分重要的意义。本论文通过共混法,制备了纳米炭黑及纳米二氧化硅复合涂料。通过增重法、失重法、阳极极化曲线法和交流阻抗法测试了纳米复合漆的防腐性能,考察了超声作用、纳米颗粒的添加量等因素对涂层耐蚀性能的影响。通过接枝法,在炭黑表面分别引入聚乙烯醇和聚丙烯酸甲酯高分子链,获得纳米尺度的亲油性接枝炭黑,透射电镜和原子力显微镜测试结果表明,粒子的平均尺寸约为63nm和74nm。以醇酸稀料为稀释剂,在超声场下将两种纳米接枝炭黑分散。通过机械搅拌和超声波共同作用,将纳米碳黑均匀分散到油漆中,制得纳米炭黑复合漆。对于接枝聚乙烯醇纳米炭黑复合漆,腐蚀增重法实验结果表明,纳米炭黑复合漆的耐蚀性优于普通漆,试片在3.5wt% NaCl溶液中的腐蚀增重减少约3/4; 从阳极极化曲线可以看出,纳米复合漆涂层的腐蚀电位正移约400mV,阳极腐蚀电流降低一个数量级以上; 交流阻抗和失重法实验也得到相同的结果。通过化学改性法,利用硅烷偶联剂(A858)与纳米二氧化硅表面的羟基发生反应,消除或减少表面硅羟基的量,使纳米二氧化硅由亲水性变为疏水性,提高了二氧化硅与涂料的相容性。原子力显微镜测试结果表明,粒子的平均尺寸约为98nm。以丙酮为稀释剂,在超声场作用下将改性后的纳米二氧化硅分散。在机械搅拌和超声波共同作用下,将纳米二氧化硅加入到油漆中,获得纳米二氧化硅复合漆。腐蚀实验测试结果表明,纳米二氧化硅粒子的加入显著提高了油漆在NaCl介质中的耐蚀性。对比不同纳米颗粒添加量的复合漆的耐蚀性发现,当纳米粒子浓度较低时,随着油漆中纳米粒子复合量的增大,纳米复合漆的防腐性能提高; 但粒子浓度太高时,纳米粒子复合量增大,纳米复合漆的防腐性能反而下降。对于接枝聚乙烯醇纳米炭黑复合漆,炭黑浓度为1wt%时耐蚀性最好; 对于接枝聚丙烯酸甲酯的纳米炭黑复合漆,浓度为0.68wt%时性能最佳; 而对于纳米二氧化硅复合漆,浓度为0.91wt%时抗蚀效果最好。通过研究接枝聚合、超声作用、纳米炭黑的添加量等因素对纳米炭黑复合更多还原

【Abstract】 Coating is the most important and economical method of all anticorrosive methods. Although there are all kinds of coatings with corrosion resistance, anticorrosive results are not very good because mechanics and chemistry cause lifetime problem. As a result, it is very significant to study a coating with high corrosion resistance. Through co-mixing, nanometer carbon black and silicon dioxide composite coatings can be prepared. Immersion corrosion testing, anodic polarization and electrochemical impedance spectroscopy (EIS) are employed to study the corrosion behavior of nanometer composite coating. The effects of ultrasonic field and nanometer-particle content on corrosion resistance of the coatings are studied. Through surface graft modification, polymethyl acrylate and polyvinyl alcohol are introduced on the surface of carbon black. Then oil-soluble carbon black nanometer particles are synthesized. SPM image and TEM picture show that the particle size is about 63nm and 74nm. Nanometer carbon black dispersion system using alkyd resin paint thinner as diluting agent is got in the ultrasonic field, and then nanometer composite coating is got through ultrasonic field and mechanical agitation. Coating of carbon black grafting polyvinyl alcohol, increasing weight corrosion experiment shows that corrosion resistance of the coating in 3.5% NaCl solution is better normal coating without carbon black grafting polyvinyl alcohol and the weight is reduced by 3/4 of the original. Anode polarization curves show that its anodic corrosion current is reduced to about 1/10 of the former, and its corrosion potential increases by about 400mV. Losing weight corrosion experiment and electrochemical impedance spectroscopy (EIS) get the same results. Through chemical modification, silane coupling agent (A858) reacts with hydroxide radical on the surface of nano-SiO2 reducing or removing hydroxide radical content. Then nano-SiO2 becomes hydrophobic, and its compatibility with coatings is improved. The SPM image shows that the particle size is about 98nm. In the ultrasonic field, modified SiO2 is dispersed in acetone. SiO2 dispersion system is added into coating, and then nanometer SiO2 composite coating is got through ultrasonic field and mechanical agitation. Corrosion experiments show that modified SiO2 improves corrosion resistance of coating in 3.5% NaCl solution greatly. Coatings with different nanometer particles content is compared, and the result is got that when nanometer particle content is low, corrosion resistance become better with the increase of nanometer particle content. But when nanometer particle content is high, the result is contrary. For the coating of carbon black grafting polyvinyl alcohol, corrosion resistance of 1wt% is the best; for the coating of carbon black grafting polymethyl acrylate, corrosion resistance of 0.68wt% is the best; for the coating of nano-SiO2, corrosion resistance of 0.91wt% is the best. Through analysis of surface graft modification, ultrasonic field and nanometer particle content effects on nanometer carbon black dispersion in coating and corrosion resistance, the composite coating corrosion resistance mechanism is studied. The corrosion resistance can be effectively improved when the nanometer carbon black can be dispersed uniformly without agglomeration. The nanometer carbon black has small grain diameter, can move in coating freely. The nanometer particles fill the defect area in coatings, improve its flexibility, and prevent ions from penetrating coating to corrode the substrate. Nano-SiO2 not only have such effects on corrosion resistance as nanometer carbon black, but also have the thixotropy that after it is dispersed, it can recombine with each other which prevents nano-SiO2 from stratifying and makes adhesion strong. In addition, modified nano-SiO2 becomes hydrophobic, which prevents corrosive things from immersing the coating film. When nano-SiO2 content is low, the nano-SiO2 can be dispersed uniformly without agglomeration, can move in coatings freely and fill the defect area in coatings, so it improves corrosion resistance. But when nano-SiO2 content is high, nano-SiO2 agglomerates and its size becomes bigger. So it can not move in coatings freely, stress concentration increases and bigger particles fall off easily, which makes corrosive things touch metal directly and corrosion resistance become worse.更多还原