Metallurgical study on electro-magnetic flow meter and pump for liquid lead-bismuth flow

Corrosion and precipitation of corrosion products at an electrode of an electro-magnetic flow meter and in a narrow channel of an electro-magnetic pump (EMP) for lead bismuth (Pb-Bi) flow was investigated by means of metallurgical analysis. The roughened surface of inlet pump core at the entrance of EMP flow channel was observed, which indicated the occurrence of the so-called corrosion/erosion. In the same time, corrosion products were precipitated on the surface of the electrode and the outlet pump core. Localized corrosion/erosion and precipitation of corrosion products were observed by means of SEM/EDX analysis for their cross sections. The surface condition was different from each other depending on the place. The precipitation products were made of double-layers, that is, an outer layer and an inner layer. The inner layer (diameter range of 0-20 mu m) contained Fe in the fraction of 99wt%, and the outer layer (diameter range of 20-40 mu m) contained Pb-Bi in the fraction of 10wt%. The double layer structure might be caused by difference of precipitation period. These lumps of the precipitation products could be the cause of the channel plugging. (C) 2005 Elsevier Ltd. All rights reserved.