Identification of steel corrosion in alkaline sulfate solution by electrochemical noise

Abstract Research on the effects of sulfate ions on steel corrosion has been conducted in response to the observations of premature localized corrosion of steel strands in cementitious grouts in posttensioned bridge construction. Electrochemical noise (EN) was shown to be an effective technique to assess the development of localized corrosion of steel in the alkaline sulfate solution. General statistics of the EN potential and current time signatures revealed the negative effect of elevated sulfate concentrations and the development of pitting events. Spectral analysis indicated an increase in the characteristic charge and decrease in characteristic frequency with sulfate ion concentration, whereas an increase in the overall corrosion rate was observed, indicating the development of pitting corrosion. Pitting events could be sustained in solutions above 10 g Na 2 SO 4 /L H 2 O and more extensive localized corrosion developed above 20 g Na 2 SO 4 /L H 2 O.