Electrochemical Study of Steel Corrosion in Saturated Calcium Hydroxide Solution with Chloride Ions and Sulfate Ions

The corrosion of Q235 carbon steel in the saturated calcium hydroxide solution containing chloride ions and sulfate ions are studied using electrochemical methods and wire beam electrode (WBE) sensor. The cyclic potentiodynamic polarization measurements showed that localized corrosion was mainly induced by the adsorption of chloride ions on the passive film. When the passive film is intact, sulfate ions are not corrosive to the passive film and it can inhibit the pitting initiation caused by the chloride ions. However, the WBE test results indicate that once a stable pit has already formed, sulfate ions cannot mitigate the pitting corrosion, and it can further promote the propagation of the major anodic area. Through the electrochemical impedance spectroscopy measurements, it can be found that the addition of sulfate ions in the solution containing chloride ions will not result in the rise of the general corrosion rate.