It was generally found that the low pressure cylinder blades of steam turbines had pitting corrosion during the overhaul of super-critical units. In order to analyze the causes of low pressure cylinder blades pitting corrosion, the corrosion products were analyzed by scanning electron microscope and energy disperse spectrometer, and the water vapor of the unit was detected by ion chromatograph. Results showed that the content of CO2 in water vapor was very small, which had little effect on the blade pitting corrosion. The main cause of pitting corrosion was the improper control of the operation end point of fine treatment mixed bed, resulting in the high chloride ion in the water vapor. It was pointed out that controlling the operation end point of fine treatment mixed bed could effectively avoid the pitting corrosion of steam turbine low pressure cylinder blades of super-critical units.
