Experimental study on passivation and corrosion performances of pre-rusted steel in simulated concrete pore solution

The influences of the rust layer on the passivation and corrosion of Q235b carbon steel in simulated concrete pore solution were studied. The differences between the inner and outer rust layer were characterized. Results show that the pre-rusted samples could still reach passive state at high pH condition free of chloride ions. However, the quality of the passive film formed on the pre-rusted steel were dramatically lower than that formed on the fine polished steel. The pitting corrosion resistance of the pre-rusted steel was significantly higher than that of the fine polished steel in the chloride-containing pore solution. The pitting corrosion potential would be further promoted after the elimination of the outer rust layer. The reaction between the hydrogen ions and the rust layer could inhibit the pitting initiation. Furthermore, the consumption of the corrosive agents induced by the rust layer could further retard the area expansion of the pits.