The Effect of Hydrazine on the Electrochemical Corrosion Potential of Steam Generator Tubing in the Presence of Oxygen

Abstract

The electrochemical corrosion potential (ECP) of steam generator (SG) tubing is governed by plant chemistry during operation. SG tubing is occasionally exposed to dissolved oxygen and CANDU stations use hydrazine to reduce the oxygen concentration. This lowers the ECP, protecting the tubing from localized corrosion known to occur under oxidizing conditions. CANDU SG tubing materials, Alloys 800 and 600, were exposed to water containing dissolved oxygen and the resulting ECP shift measured. Subsequently, hydrazine additions were made. The ECP was monitored continuously and the effectiveness of different hydrazine concentrations in restoring the ECP to its original value was determined.