The role of temperature on the corrosion and passivation of type 310S stainless steel in eutectic (Li + K) carbonate melt

The corrosion behavior of type 310S stainless steel was studied in the eutectic Li + K carbonate as a function of temperature by several electrochemical methods. Within the range 600–675 °C the steel passivated spontaneously at OCP condition after a few hours of immersion. Active-passive transition was observed in the polarization curves below 600 °C and above 675 °C indicating a failure to reach a stable passive condition even at prolonged exposure times. Impedance analysis indicates that passivity does not lead to the formation of an impervious barrier layer as denoted by the presence of diffusional components at low frequencies indicating oxide growth. Corrosion rates exhibited a minimum at 675 °C at both OCP and at cathode polarization conditions. A mechanism to explain the active–passive transition has been proposed based on the phase transition from LiFe5O8 to LiFeO2.