碳钢表面磷酸镁水泥涂层的防腐性研究

发布时间：2018-05-10 20:31

本文选题：磷酸镁水泥 + 电化学　；参考：《西南交通大学》2017年硕士论文

【摘要】：磷酸镁水泥(MPC)以早强快硬、环境适应性强、粘结强度高、耐久等优异性能而被广泛应用于快速修补、废料封存领域。现有研究已对磷酸镁水泥的水化机理、缓凝机理、微观结构、原料配比、掺杂改性力学性能、耐久性进行大量探究,但大多以其块状混凝土试样为研究对象。国外学者尝试将磷酸镁水泥用于金属基体表面防护,并取得了良好效果,而国内研究很少。因此,本文尝试用电化学测量技术探究碳钢表面磷酸镁水泥涂层的耐腐蚀性能。本论文在45号钢表面制备MPC水泥涂层,并评价其耐腐蚀性和耐腐机理。论文第二章,在喷砂、磷化后的45号钢表面用不同手工涂刷方式,制备一层厚约500 μm不同镁磷比(M/P)的磷酸镁水泥涂层。再采用短期电化学阻抗谱和线性极化法,对比M/P分别为3/1、4/1、5/1的磷酸镁水泥的电化学特性,实验结果表明M/P为5/1时磷酸镁水泥涂层阻碍电荷转移的作用力最大。随后对比单次涂刷和多次涂刷对涂层性能的影响,结果显示多次涂刷更有利于涂层对金属基体的防护。论文第三章选择M/P为5/1的MPC多次涂刷于磷化后45号钢表面,并用SEM、XRD、较长期的线性极化法、电化学阻抗谱,长期的盐雾试验和粘结实验表征涂层的防腐蚀性。结果表明MPC涂层由致密棱柱状晶堆积而成,内部有少量微裂纹,主要成分为MgKPO_4·6H_2O、MgO和Al_2O_3。试样浸泡1 h至12 d的R_p基本维持在2.0×10~5 Ω·cm~2,Rc 始终保持在8×10~4 Ω·cm~2左右,表明涂层可能有长期有效的防腐作用。且试样在盐雾箱中放置150 d后表面也未现腐蚀产物,粘结实验结果显示其粘结强度为4.8±0.7 MPa,进一步证明MPC可作为45号钢表面长期稳定的耐腐蚀涂层。论文第四章通过浸泡试验和动电位极化法分析了 MPC涂层的耐腐蚀机理。结果显示,浸泡在3.5%NaCl+MPC溶液中的试样腐蚀程度最低,开路电位最稳定,且极化曲线自腐蚀电位向正方向移动,阳极分支明显下降。表明MPC内未完全反应的MgO和微溶磷酸盐对45号钢有阳极缓蚀作用。因此,MPC涂层为45号钢提供物理阻隔和化学缓蚀双重防腐蚀作用。
[Abstract]:Magnesium phosphate cement (MPC) has been widely used in the field of rapid repair and storage for its excellent properties such as early strength and quick hardening, strong environmental adaptability, high bond strength and durability. The hydration mechanism, retarding mechanism, microstructure, ratio of raw materials, doping modified mechanical properties and durability of magnesium phosphate cement have been studied extensively, but most of them take its block concrete sample as the research object. Foreign scholars have tried to use magnesium phosphate cement as surface protection of metal matrix, and achieved good results, but there are few researches in China. Therefore, the corrosion resistance of magnesium phosphate cement coating on carbon steel was investigated by electrochemical measurement technique. In this paper, MPC cement coating was prepared on 45 # steel and its corrosion resistance and corrosion resistance mechanism were evaluated. In the second chapter, a layer of magnesium phosphate cement coating with thickness of about 500 渭 m and different ratio of magnesium to phosphorus is prepared on the surface of 45 steel after sand blasting and phosphating by different manual brushing methods, and the coating thickness is about 500 渭 m and the ratio of magnesium to phosphorus is about 500 渭 m. The electrochemical characteristics of magnesium phosphate cement with M / P = 3 / 1 / 4 / 1 / 5 / 1 were compared by short term electrochemical impedance spectroscopy and linear polarization method. The experimental results show that when M / P is 5 / 1, the interaction force of magnesium phosphate cement coating hinders charge transfer is the largest. Then, the effects of single and multiple brushes on the coating properties were compared. The results showed that the multiple brushing was more favorable to the protection of the coating on the metal substrate. In the third chapter, MPC with M / P = 5 / 1 was chosen to brush the surface of 45 steel after phosphating many times. The corrosion resistance of the coating was characterized by SEMX XRD, linear polarization method, electrochemical impedance spectroscopy, long term salt spray test and bonding experiment. The results show that the MPC coating is composed of dense prismatic crystals with a small number of microcracks, and the main components are MgKPO_4 6H _ 2O _ 2O _ (MgO) and Al _ 2O _ 3 _ 3. When the samples were soaked for 1 h to 12 days, the RSP remained at about 8 脳 10 ~ (4) 惟 cm~2, indicating that the coating may have a long-term and effective anticorrosion effect. Moreover, no corrosion products were found on the surface of the specimen after being placed in the salt spray box for 150 days. The bond strength of the specimen was 4.8 卤0.7 MPA, which further proved that MPC can be used as a long-term stable corrosion resistant coating on 45 steel. In chapter 4, the corrosion resistance mechanism of MPC coating was analyzed by immersion test and potentiodynamic polarization method. The results show that the sample immersed in 3.5%NaCl MPC solution has the lowest corrosion degree, the most stable open circuit potential, and the polarization curve moves in the positive direction from the corrosion potential to the anode branch. It is shown that MgO and microsoluble phosphate in MPC have anodic inhibition on 45 steel. Therefore, MPC coating provides both physical barrier and chemical corrosion inhibition for 45 steel.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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