Evaluation of Chloride Ion Concentration and pH on Depassivation of Steel Rebar in Concrete Investigated by Electrochemical Impedance Measurement of Probe Electrodes

The relationship between chloride ion concentration and pH on de-passivation of steel rebar embedded in concrete was investigated by a two frequencies impedance measurement using probe electrodes. A saturated calcium hydroxide solution used for the electrolyte as simulated pore solution. pair electrodes, which simulates rebar, immersed prepared an arbitrary ions, performed. Air supplied to simulate neutralization during measurement. charge transfer resistance related electrode/solution interface, Rct, estimated from electrodes each This demonstrated that Rct drastically reduced decreasing solution, namely, rebar. corrosion conditions were categorized “passive state,” “de-passivation,” “corrosion” based changes monitoring These results plotted two-dimensional diagram composed passive film discussed.