Comparative studies on passivation and corrosion behaviors of two types of steel bars in simulated concrete pore solution

The corrosion behavior of two types of stirrups, a plain steel bar and a ribbed steel bar, were studied in this work. The results demonstrated that a better passive state was achieved on B500, which was due to a relatively higher concentration of Fe²⁺ oxides at the first 2 nm depths of the film, even though B500 film had relatively less FeO_x contents, because Fe²⁺ oxides had a better protective property than Fe³⁺ oxides. Furthermore, the slightly lower donor density of B500 film in the M-S analysis results presented the much less point defect in the film, showing an increase in the anti-corrosion property of passive film. These contributed to a higher chloride threshold value of B500, 4 times higher than that of S275. Therefore, compared with S275, B500 stirrups could be more suitable for the application in the severe service environment.