Comparisons of the Oxide Layer Between Static Liquid-Bismuth-Eutectic and Gas Environments

The competition between corrosion and oxidation on a steel surface immersed in lead alloys with controlled oxygen leads to different oxide-layer characteristics as compared with those formed in gases. The presence of a liquid metal [liquid lead or lead-bismuth eutectic (LBE)] can either enhance or reduce the oxidation rate, resulting in different oxide growth rates and microstructures. Based on analysis of experimental results in static LBE/lead and gases under the same experimental conditions, we predict the oxide-layer structure and thickness as functions of immersion time and analyze the factors that play important roles in the oxidation process in LBE/lead. It is shown that there is a significant difference between the oxide formed in liquid lead alloys and in gases, including the oxide-layer structure. To generate a stable protective oxide layer on steel surfaces in LBE, the long-term corrosion effect, the supply of oxygen, and the penetration of the liquid metal into the structural materials or oxide layers must be taken into account. (authors)