Effect of chloride and sulfate ions in simulated boiler water on pitting corrosion behavior of 13Cr steel

• The influence of Cl− and SO42− on pitting corrosion behavior was investigated.
• Pit initiation was inhibited by the addition of SO42− into the water containing Cl−.
• Pit growth was also suppressed by the presence of 50 ppm SO42− with 100 ppm Cl−.
• The addition of 100 ppm SO42− with 100 ppm Cl− promoted pit growth conversely.

The pitting corrosion behavior of 13Cr steel was investigated in simulated boiler waters containing chloride ions (Cl−) and sulfate ions (SO42−) using potentiodynamic and potentiostatic polarization tests in addition to pit morphology analysis. The presence of 100 ppm Cl− in the water caused pitting corrosion of the steel. Pit initiation was inhibited by the addition of 50 ppm or 100 ppm SO42− into the water containing 100 ppm Cl−. Pit growth was also suppressed by the presence of 50 ppm SO42− in the water with 100 ppm Cl−; however, it was conversely promoted in the presence of 100 ppm SO42−.