Copper dissolution and electrochemical behavior in EDTA- and EDA-based solutions for steam generator chemical cleaning

Copper dissolution and electrochemical behavior have been investigated in order to find out which parameters are critical and important during the two major copper removal processes for chemical cleaning of nuclear steam generator and to evaluate safety aspects and effectiveness of these processes. Hydrogen peroxide was very effective for the process using EDTA-based solution at 38 degreesC to control the corrosion potential of copper into an optimum potential range from -0.3 to +0.2 V for copper sludge dissolution. Corrosion rates of carbon steel SA 285 Gr.C and Alloy 600 were very small in this potential range. The process using EDA-based solution at 60 degreesC was effective to dissolve copper sludge if the corrosion potential of copper could be controlled above -0.3 V. However, it was very difficult under the laboratory conditions to raise its corrosion potential to this range by air blowing and stirring. (C) 2003 Elsevier Science B.V. All rights reserved.