Control of chloride ion corrosion by MgAlO_x/MgAlFeO_x in the process of chloride deicing

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 MgAlO_x or MgAlFeO_x depending on the preparation element. By analyzing the removal efficiency and the freezing point of MgAlO_x and MgAlFeO_x to Cl^-, the feasibility of the study was determined. Resulted that the removal efficiency to Cl^- of MgAlFeO_x at low temperature (0 ± 2 °C) and room temperature (25 ± 2 °C) was higher than that of MgAlO_x, reaching 39.4% and 85.60%, respectively. And the freezing point of MgAlFeO_x was lower than that of MgAlO_x, the value was -12.0 °C. At the same time, we also found that CaCl₂-MgAlO_x and CaCl₂-MgAlFeO_x significantly reduced the corrosion of carbon steel and concrete compared with chloride salts, and CaCl₂-MgAlFeO_x had the lowest corrosion degree. Hence, MgAlFeO_x 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 MgAlFeO_x after Fe³⁺ was added, and the mechanism of corrosion inhibitors was further determined that was achieved by adsorption and neutralization.