Influence of pH on the nitrite corrosion inhibition of reinforcing steel in simulated concrete pore solution

Measurements of corrosion rate of reinforcing steels have been carried out in solutions simulating electrolytic chloride environments in corrosion pits in the propagation period with sodium nitrite. A significant corrosion inhibition has been observed at relatively low chloride contents of 0.045 M due to the presence of nitrite in these systems, but its efficiency decreases when the pH is reduced. The corrosion intensity seems to be related to the [Cl−]/[OH−] ratio. Three different pH regions from acid to alkaline have been observed in terms of corrosion activity. An explanation on the behaviour of nitrite at different pH is given.

► NaNO2 was tested as steel corrosion inhibitor in solutions with different pH.
► Initial stage of propagation period was simulated by Ca(OH)2 and FeCl2 solutions.
► A NaNO2 concentration of 0.1 M shows better performance than 0.5 M.
► A NaNO2 concentration of 0.5 M can even increase corrosion rate of steel.