Abstract
In secondary coolant system of the pressurized water reactors, the reduced corrosion products such as metallic Cu and Pb particles were accumulated in the pores of the magnetite flakes and electrically contacted to the steam generator materials. The micro-galvanic corrosion behavior of steam generator materials (steam generator tube materials: Alloy 600 and Alloy 690, steam generator tube sheet materials: SA508 Gr.3) contacted to the corrosion products (magnetite, Cu, and Pb) was investigated in an alkaline solution. The steam generator materials considered in this study were all the anodic elements of the galvanic pair because their corrosion potentials were lower than those of the corrosion products. The corrosion rate of the steam generator materials was increased by the galvanic coupling with the each corrosion products, and was more accelerated with increasing the area ratio of the corrosion products to the steam generator materials. Among the corrosion products, Cu has the largest galvanic effect on steam generator materials in the pores when area ratio of cathode to anode is 10.
Highlights
In nuclear power plants, Fe ions were released from the surface of carbon steel piping and were combined with dissolved oxygen to form a magnetite in a secondary coolant system of the pressurized water reactors (PWRs)
The galvanic corrosion of steam generators (SGs) materials (Alloy 690, Alloy 600, SA 508 Gr.3) within the micro-pores of magnetite flakes was investigated in an alkaline solution using the electrochemical corrosion tests
The magnetite flake samples removed from an operating SG were characterized to identify the various corrosion products accumulated in the pores of the flakes
Summary
Fe ions were released from the surface of carbon steel piping and were combined with dissolved oxygen to form a magnetite in a secondary coolant system of the pressurized water reactors (PWRs). Many investigations on the galvanic effect by magnetite on the corrosion behavior of secondary coolant system materials such as nickel-based alloys [4,5,6] and carbon steel [7,8,9] have been reported. Cu and Pb in secondary water of PWRs. there are few studies for the effect of Cu and Pb on the galvanic corrosion of SG materials in the simulated secondary water of PWRs. In addition, there is no research comparing the degree of galvanic effect by the various corrosion products (magnetite, Cu, and Pb) constituting SG deposits. The micro-galvanic corrosion behavior of SG materials (SG heat exchanger tube materials: Alloy 600 and Alloy 690, SG tube sheet materials: SA508 Gr.3) in pores formed on the magnetite flakes was investigated in an alkaline solution. The electrochemical corrosion parameters of SG materials and the corrosion products (magnetite, Cu, and Pb) were measured in the alkaline solution through the various electrochemical corrosion techniques
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