Corrosion behavior of 316 stainless steel arc parts in liquid lead at 650 °C under high oxygen concentrations

Abstract

The corrosion of 316SS in contact with lead complicates the realization of high coolant temperature. To explore the corrosion behavior at high temperature, the corrosion test of 316SS was performed in liquid lead at a high temperature of 650 °C under Ar with oxygen levels of 10⁻² wt% and 10⁻⁵ wt% by the static corrosion method. The mass changes after corrosion were determined; then, the corrosion depth and the oxide product formed were further characterized. A multi-oxide layer was formed on the 316SS alloy surface, and the thickness reached 17.5 μm over a period of 100 h at the oxygen level of ∼10⁻² wt%. Fe oxide was the main product in the outer layer; the dense Fe–Cr oxide was formed in the inner layer and lead was isolated from the metal substrate. When the oxygen content was 10⁻⁵ wt%, corrosion by dissolution at a rather high rate was dominant, and the corrosion depth was as high as 50 μm for 100 h. It is speculated that the oxide layer is also formed at the initial stage but gets dissociated when there is no oxygen supply to sustain the oxide layer with prolonged exposure time. The oxygen content in the cover gas greatly influences the corrosion behavior of 316SS, thus directly affecting the application of 316SS immersed in liquid lead at high temperature.