The electrical impedance response of steel surface oxide layers in molten lead–bismuth eutectic

Stainless steel 316L samples were preoxidized and then immersed in molten lead–bismuth eutectic (LBE) alloy at 200 °C. The changes in their electrical impedance responses were observed over time. Negligible impedance magnitudes were observed at first, followed by a rapid increase to thousands of ohm-cm2. The impedance response is sensitive to changes in the immersed sample area. Micro-indentations on samples caused their impedance magnitudes to decrease initially, but the magnitudes recovered within a few days. SEM analysis showed that the indentations were still present and visible even after the recovery of impedance response, demonstrating that the physical features of the oxide layers which govern the electrical response must be smaller than the micrometer length scale.