Effects of Chloride and pH on Passivation Characteristics of Q235 Steel in Simulated Concrete Pore Solution

The impact of chloride and pH on the passivation and corrosion behavior of Q235 steel in simulated concrete pore solutions was studied by different electrochemical methods. Mott-Schottky test results demonstrated that the passive film of Q235 steel showed n-type semiconductor behavior, with two different donor densities at pH 13. As the chloride concentration is increased the donor density is also elevated, resulting in elevated disorder and number of impurities present in the passive film. The electrochemical impedance spectroscopy results indicated that as the chloride concentration was increased the electric double layer capacitance also increased and the charge transfer resistance decreased. This was indicative of the corrosion resistance properties of the passive film decreasing. As the pH value is reduced the passive film will undergo corrosion at lower chloride concentrations, with the passive film becoming more susceptible to corrosion. A highly alkaline solution can provide better protection for steel in the presence of chloride.