Effect of Sulfate and Chloride ions on pitting corrosion behavior of 2Cr12MoV Steel at pH 6 and 90 °C

Abstract

The effect of SO42- on the pitting corrosion behavior of 2Cr12MoV Steel in early condensates containing Cl- was studied by electrochemical measurements, scanning electron microscopy and energy dispersive X-ray spectroscopy. The potentiodynamic polarization results show SO42- suppressing the pitting corrosion initiation on 2Cr12MoV steel. Potentiostatic polarization, SEM and EDS analysis results show SO42- has effect on suppressed pits initiated by competitive absorption with Cl- and pits growth by forming low solubility salts with metal ions inside the pits and covered on the pit mouths. The effect of SO42- on suppressed pits growth reduced with 10 ppm SO42- added into test solution compared to 5 ppm SO42- added due to cracks appeared on the corrosion products film, which enabled pit growth to continue.