Interpretation of impedance data for reinforcing steel in alkaline solution containing chlorides and acetates

Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were used to study the corrosion of reinforcing steel in a simulated pore solution with and without additions of chloride ions (0.5 M KCl), and calcium magnesium acetate (CMA) (0.2 M). The latter is considered as a possible deicing agent. Under open-circuit conditions, the initial rest potential (E_r) shifted in the noble direction and the charge transfer resistance (R_ct) increased, but after a few days E_r moved in the negative direction and simultaneously R_ct decreased, whereas the double layer capacitance (C_dl) and depression angle of the charge transfer semicircle increased. R^-1_ct rose with increasing C_dl. The impedance and voltammetric measurements indicated that the addition of CMA to the simulated pore solution diminished the corrosion rate and increased the protectiveness of surface films.