NO3-/NO2-插层MgAl-LDHs在混凝土模拟孔溶液中的阻锈性能

通过共沉淀法合成硝酸根插层镁铝层状双金属氢氧化物MgAl-NO3 LDHs（简称LDHs-NO3），以其为主体，由离子交换制备亚硝酸根插层双金属氢氧化物MgAl-NO2 LDHs（简称LDHs-NO2）.通过对比试验，采用等温吸附法、自腐蚀电位和电化学阻抗谱（EIS）研究所制备的LDHs-NO3、LDHs-NO2在混凝土模拟孔溶液中对氯离子的吸附性能及其对钢筋的阻锈作用；采用扫描电镜（SEM）、X射线衍射（XRD）和傅里叶变换红外光谱（FTIR）揭示其阻锈机理.结果表明：LDHs-NO2的最大氯离子吸附量为2.51 mmol/g，与LDHs-NO3相差不大，展现出良好的氯离子吸附性能；LDHs-NO2具有比LDHs-NO3更好的阻锈效果，可以明显提高钢筋在混凝土模拟孔隙液中的临界氯离子浓度值；LDHs-NO2良好的阻锈性能源于对氯离子的吸附和阻锈离子NO2-的释放，对钢筋产生双重阻锈作用，同时有效阻锈成分NO2-逐步释放，可以为钢筋提供长期的保护作用.
Abstract: Mg-Al-NO2 LDH (LDHs-NO2) was synthesized by anion exchange in the host materia; Mg-Al-NO3 LDH (LDHs-NO3) was prepared by coprecipitation method. By a comparative experiment, the inhibitive effect of LDHs-NO3 and LDHs-NO2 on the corrosion resistance performance of steel in simulated concrete pore solution were investigated by means of chloride equilibrium isotherm, corrosion potential and electrochemical impedance spectroscopy (EIS). Besides, scanning electron microscopy (SEM), X-ray diffraction instrument (XRD) and infrared spectroscopy were applied to observe the morphologies and microstructures of LDHs. Results show that the maximum chloride adsorption capacity of LDHs-NO2 is 2.51 mmol/g, which is similar with that of LDHs-NO3, indicating good adsorption property of chloride ion; LDHs-NO2 has better inhibition effect than LDHs-NO3, which can significantly increase the chloride threshold value of steel in the simulated concrete pore solution. The good anti-corrosion performance of LDHs-NO2 is because of the chloride ions adsorption and the release of NO2- in the interlayer, which provides dual effect of anti-corrosion performance for steel bar. At the same time, the effective corrosion resistance component NO2- is released gradually, which can provide long-term protection for steel bar.