Corrosion behavior of steel bars in simulated concrete pore solution under the coupling action of chloride salt and DC stray current

Abstract

The stray current generated during the operation of rail transit projects located in coastal and saline soil areas often makes the concrete structures along the line in a deteriorating environment with the coexistence of chloride salt and stray current, which significantly accelerates the corrosion process of steel bars and endangers the safety of engineering structures. In this paper, the depassivation behavior and corrosion behavior of steel bars in simulated pore solution under the combined action of low DC stray current and chloride ion were studied by electrochemical method. The results show that when the DC stray current and chloride ion coexist, the steel bar is easy to depassivate, and the two promote each other, the coupling effect is obvious. At a constant chloride ion concentration, the pH, chloride ion concentration of the corrosive medium and current density will affect the corrosion current efficiency. In the high pH environment, the current efficiency gradually increases with the increase of chloride ion concentration, but as the pH decreases or the chloride ion concentration continues to increase, the current efficiency is slightly greater than 1.0. When the concentration of chloride ions is inconsistent, the higher the concentration of chloride ions in a local area, the more severe the corrosion of the rebar in that area. The difference in resistance between the steel bar and the cathode caused by the concentration difference of chloride ions is the main reason for the different electricity consumption in each region and the overall uneven corrosion.