Effect of sodium nitrite on the carbon steel corrosion inhibition in the aerated neutral (pH 7) and alkaline (pH 11) water solutions at temperatures from 30o C to 140o C has been investigated by mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy methods. Sodium nitrite was added in concentrations: 200, 350, 500, 750, 1000, 1500 and 2000 ppm by mass.