Abstract
Adding a corrosion inhibitor to the chloride deicing salt can prevent the corrosion and pollution of Cl-, which is very important. Layered double hydroxide (LDHs), calcined at high temperature is used as adsorbents to remove various anionic contaminants, and it can reduce the freezing point of solution after adsorbing anions. Therefore, this paper reports the use of calcined LDHs as corrosion inhibitors in deicing salts, which are denoted as MgAlOx or MgAlFeOx depending on the preparation element. By analyzing the removal efficiency and the freezing point of MgAlOx and MgAlFeOx to Cl-, the feasibility of the study was determined. Resulted that the removal efficiency to Cl- of MgAlFeOx at low temperature (0 ± 2 °C) and room temperature (25 ± 2 °C) was higher than that of MgAlOx, reaching 39.4% and 85.60%, respectively. And the freezing pointof MgAlFeOx was lower than that of MgAlOx, the value was -12.0 °C. At the same time, we also found that CaCl2-MgAlOx and CaCl2-MgAlFeOx significantly reduced the corrosion of carbon steel and concrete compared with chloride salts, and CaCl2-MgAlFeOx had the lowest corrosion degree. Hence, MgAlFeOx was chosen as the corrosion inhibitor in chloride deicing salt. The metal molar ratio, synthesis temperature, and calcination temperature for preparation of MgAl/MgAlFe-LDHs were determined by XRD and TG-DSC analysis that were 9/2/1, 120 °C, and 500 °C, respectively. Characterization methods such as Zeta, XRD, XPS, BET, and SEM were used to study in detail the characteristic changes of MgAlFe-LDHs and MgAlFeOx after Fe3+ was added, and the mechanism of corrosion inhibitors was further determined that was achieved by adsorption and neutralization.
Highlights
In order to prevent or mitigate the traffic influence and hazards caused by snowfall in winter, it is necessary to quickly remove snow and ice from the road surface
It can be seen from the analysis curve that there are three endothermic peaks, indicating that the thermal decomposition of MgAlFe-LDHs is mainly divided into three parts (It can be seen from the analysis curve that the thermal decomposition of MgAlFe-LDHs is mainly divided into three parts) ( Ji et al 2017)
The first absorption peak rises from 30 °C to about 258 °C, mainly caused by the removal of water molecules adsorbed on the surface and between the layers
Summary
In order to prevent or mitigate the traffic influence and hazards caused by snowfall in winter, it is necessary to quickly remove snow and ice from the road surface. Due to the small ionic radius, chloride ions penetrates into the concrete with the solution, achieving the purpose of breaking the internal structure of the concrete and corroding the metal surface. This is a long-term cumulative process (Farnam et al 2015a). It is necessary to reduce the corrosion of the infrastructure on the basis of ensuring rapid deicing of the mixed deicing salt. Many researchers have done a lot of research on the corrosion inhibitors in deicing salt, and it is concluded that the addition of corrosion inhibitors greatly reduces the erosion of Cl(Farnam et al 2015b; El-Nahhal et al 2005)
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