Micro-Galvanic Corrosion of Steam Generator Materials within Pores of Magnetite Flakes in Alkaline Solutions

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.