APPLICATION OF ELECTROCHEMICAL TECHNIQUES TO CORROSION CONTROL IN FEEDWATER AND BOILER SYSTEMS

摘要

Corrosion monitoring tests were carried out to examine the applicability of electrochemical techniques into corrosion control at a fossil power plant operated with Oxygenated Treatment (OT). A once-through type subcritical pressure boiler was employed to corrosion monitoring tests, and its electric capacity is 125 MW. An autoclave system was installed at the inlet of the economizer. The temperature and pressure in the autoclave were maintained at 215 °C and 7 MPa in the case of the full load operation. The corrosion rate of carbon steel was measured under the oxygenated water condition and All Volatile Treatment (AVT) condition using a modified galvanic couple electrochemical technique and the polarization resistance method. The galvanic current and the polarization resistance were varied with the daily load fluctuations of the plant and were corresponded with the corrosion rate of carbon steel obtained from weight loss measurements. These electrochemical measurement test results suggest that these techniques are applicable to the corrosion monitoring under these conditions, and that the galvanic couple method has advantages compared with the polarization resistance method in respect to the accurate and the instantaneous corrosion rate measurement.