EFFECT OF NO<SUB>2</SUB><SUP>-</SUP> AND Cl<SUP>-</SUP> ON THE CORROSION BEHAVIOR OF REINFORCING STEEL IN SIMULATED CONCRETE PORE SOLUTIONS

Abstract

Under normal conditions, reinforcing steel in concrete maintains its passivity because of the high alkalinity of the concrete pore solution. However, steel passivity may be broken and the steel corrosion takes place due to concrete carbonation and/or chloride ingress. In fact, premature failure of reinforced concrete structures due to the steel corrosion has been a major problem in civil engineering. Therefore, the study of corrosion and protection of reinforcing steel is of indispensable importance to prolonging the service life of reinforced concrete structures. The application of inhibitors is an effective and economical method to prevent the corrosion of reinforcing steel. NaNO2 is a notable corrosion inhibitor which is effective in the steel corrosion control by reacting with ferrous ions to form a protective ferric oxide film on the steel surface, but unfortunately it can also accelerate the steel corrosion when the amount of nitrite is insufficient in amedium. In the present work, the linear polarization and electrochemical impedance spectroscopy were used to study the effect of nitrite and chloride ions on the corrosion behavior of reinforcing steel in simulated concrete pore solutions with different pH values. The results showed that the corrosion resistance of reinforcing steel is related with the pH value of the solution, nitrite ion concentrations and chloride ion concentrations. The drop of pH value and the increase of chloride ion concentration would result in the decline of corrosion resistance of reinforcing steel in the solution. The corrosion rate of reinforcing steel decreased with the NO 2 concentration increasing in the simulated concrete pore solutions with Cl , and the NO 2 ions had a good inhibiting effect on the steel when the concentration ratio of NO 2 and Cl was 0.4 or higher for the solutions of pH=12.50 or pH=10.50.