Effects of pH-value and Chloride Ion Concentration on Passivation Behavior of Steel Rebar in Different Surface Conditions

Electrochemical experiments were used to study the passivation behavior of the steel rebars with polished surface, oxide skin and rusty skin in simulated concrete pore solution. The results indicated that after the corrosion potential became stable, the steel rebar with nude surface had the highest potential while the steel rebar with rusty skin had the lowest potential. With the decrease of solutions' pH value, the passivation of the three kinds of rebar decreased. The passivation of nude surface steel rebar and oxide skin rebar was apparently better than that of rusty skin rebar. The threshold pH values for polished steel rebar, oxide skin rebar and rusty skin rebar were 11.2, 11.0 and 12.4, respectively. With the increase of chloride ion concentration, the passivation property of the three kinds of rebar decreased. The passivation of rusty rebar was apparently worse than that of nude surface rebar and oxide skin rebar. The threshold of chloride ion concentration for polished steel rebar, oxide skin rebar and rusty skin rebar were 0.03 mol/L, 0.03mol/L and 0.01mol/L, respectively.