Exploring the Effect of Deicing Salts Used in Highway Maintenance on the Electrochemical Corrosion Behavior of Mild Steel in 3.5 wt.% NaCl Solution

Deicing chemicals are widely used for maintenance of highways in winter. In this regard, sodium chloride (NaCl) is the main deicer which is applied in large-scale due to its high efficiency at commonly experienced temperatures and low cost. Other deicing agents such as CaCl2, MgCl2, and calcium magnesium acetate (CMA) are other chemicals utilized for improving the deicing performance of NaCl. However, these materials have side effects on the roadway and environment. Indeed, the deicers have detrimental effects on concrete infrastructure via interacting with concrete paste and reducing the integrity and strength of concrete; encouraging the diffusion of moisture, oxygen and other aggressive agents onto rebar surface and promoting the rebar corrosion [1-3]. Therefore, in this research, the effect of deicing salts including CaCl2, MgCl2, CMA, and urea on corrosion behavior of mild steel substrates in corrosive electrolyte is considered. The prepared electrolyte consists of 3.5 wt.% NaCl solution containing 0, 0.05, 0.1, 0.3, and 0.8 wt.% deicing salts. The corrosion performance of samples is studied by potentiodynamic polarization tests. The results indicate that the type and the concentration of deicing salt are two important parameters affecting the corrosion behavior of mild steel. The presence of other deicing salts such as CaCl2, MgCl2, and urea increases the corrosion rate of mild steel in NaCl solution. This behavior can be attributed to decrease of pH and providing chloride ions which can reduce the passive protection. However, the corrosion rate of samples in electrolyte containing 0.05 wt.% CMA increases and then, the corrosion rate decreases by adding extra amount of CMA. The corrosion rate of mild steel in 3.5 wt.% NaCl solution containing 0, 0.05, 0.1, 0.3, 0.8, 1.5, 3, and 5 wt.% CMA is 0.1152, 0.1564, 0.1611, 0.1290, 0.0886, 13th Annual Electrochemistry Seminar of Iran Materials and Energy Research Center (MERC), 22- 23 Nov, 2017 290 0.0401, 0.0670, and 0.0857 mm/year, respectively; i.e. the NaCl solution loaded with 1.5 wt.% CMA shows the lowest corrosion rate. Indeed, both calcium hydroxide and magnesium hydroxide precipitate via adding low amounts of CMA, leading to decrease of pH and reducing the passive protection. By adding extra amount of CMA, fully passive condition is attained and the corrosion rate decreases. It is believed that the results of this research will show corrosion aspects of deicing agents used in highways.