Steel corrosion in simulated concrete pore solutions using a galvanostatic pulse method

Corrosion behaviors of steel in simulated concrete pore solutions with different pH values were investigated by means of a galvanostatic pulse method(GPM).The polarization resistance of steel was derived from time constant and double layer capacitance in GPM.The time constant value of passive steel is higher than that of active steel,while the double layer capacitance of passive steel is relatively lower than that of active steel.The better anti-corrosion capacity in the final corrosion period confirms that the steel exposed to CP solution(pH 13.6) has a better passive film than that exposed to CH solution(pH 12.5),but there is not any passive film on the steel exposed to CN solution(pH 11.0).The addition of SO₄^2- and SiO₃^2- into CP solution increases the polarization resistance,promoting the passivation of steel,especially in the corrosion period.Finally,the polarization resistance values measured by GPM were compared with the results of linear polarisation resistance(LPR) and electrochemical impedance spectroscopy(EIS).It is found that the correlation is acceptable for these electrochemical methods in evaluating the corrosion rate of steel in simulated concrete pore solutions.