STUDY OF SODIUM NITRATE AND CALCIUM NITRATE AS INHIBITORS OF STEEL CORROSION IN CONCRETE

The object of this study was to assess the performance of sodium nitrite and calcium nitrate added to concrete to inhibit corrosion of reinforcing steel. These inhibitors were introduced in a (fresh concrete) mix made of 400 km/cu m Portland cement, with a water-cement ratio of 0.4. Tests were then conducted with reinforced concrete specimens. After immersion in a salt solution during one year, specimens were evaluated for the condition of the reinforcing steel. This performance of steel was assessed by electrochemical impedance spectrosocpy (EIS). The results obtained showed that: (a) both inhibitors have a protective effect if their content is not less than 6%; (b) sodium nitrite and calcium nitrate are anodic inhibitors. This means that steel half-cell potential in concrete is less negative in the presence of these compounds; (c) sodium nitrite reacts with steel and does not form a simple film on it. (A) For the covering abstract see ITRD E106702.