Oxygen-driven de-alloying of Fe-14Cr-12Ni-10Mn-3Cu-2.5Al-1Nb austenitic steel at 500 °C in static Pb-Bi eutectic with concentration of dissolved oxygen alternating from ∼10-6 to 10-9 mass% for 10000 h

• 10,000 h exposure at 500 C to static Pb-Bi is achieved for high-Mn Al-alloyed steel • Steel corrodes with leaching of Ni, Mn, Fe, Cu and Cr into the liquid metal • Oxygen, dissolved in liquid metal, traps Mn and Cr from the liquid solution due to oxide precipitation • Oxygen-driven dealloying of steel by Mn and Cr takes place A high-Mn austenitic steel Fe-14Cr-12Ni-10Mn-3Cu-2.5Al-1Nb was tested at 500 °C in static Pb-Bi eutectic for 10000 h. In the course of the test, oxygen concentration in liquid metal was cycled from ∼10 -6 to ∼10 -9 mass%, which provides oxidation and dissolution regimes, respectively. After 10000 h exposure steel showed formation of ferrite corrosion zone depleted in Mn, Ni, Cu, Cr, Fe and penetrated by Pb and Bi. Average depth of corrosion is 15±5 µm, while maximum corrosion depth locally reaches ∼35 µm. Dissolved Mn and Cr re-precipitated in the vicinity of steel surface in a form of stratified Mn-O/Cr-Mn-O oxide scale. Obtained results were compared to those of similar Al-alloyed austenitic steels with lower Mn content, which exhibited protective oxidation under same test conditions. The phenomenological mechanism of oxygen-driven de-alloying of steel in Pb-Bi[O] is discussed. High-Mn austenitic steel Fe-14Cr-12Ni-10Mn-3Cu-2.5Al-1Nb interacts at 500 °C with oxygen-containing liquid Pb-Bi eutectic with leaching of Ni, Mn and Cr from steel by the liquid metal followed by the reaction of dissolved Mn and Cr with oxygen in the melt which results in re-precipitation of reaction products in the view of the Mn-Cr layered oxide near the corroded substrate of steel.