Reformation of protective oxide layers on artificially abraded surfaces of FeCrAl alloy during 4000 h exposure in flowing lead-bismuth eutectic

Kondo, Masatoshi*; Kitamura, Yoshiki*; Kawarai, Atsushi*; Saito, Shigeru   ; Obayashi, Hironari  

The corrosion resistance of FeCrAl alloy APMT (Fe-21Cr-5Al-3Mo) in flowing lead-bismuth eutectic (LBE) was investigated by corrosion tests performed at 723 K using a non-isothermal forced convection loop. The oxygen concentration in flowing LBE was controlled at 110 wt%. No severe corrosion or erosion was detected on the specimens exposed to flowing LBE for 2000 h and 4000 h. Multiple oxide layers consisting of Fe-rich, Cr-rich and Al-rich sub-layers were formed in situ on the surface of APMT during the corrosion tests, which effectively suppressed corrosion and erosion. The oxide layers were intentionally removed by gentle abrasion prior to re-immersion and the specimens were then re-immersed in flowing LBE for an additional 2000 h. The oxide layers were spontaneously re-formed in situ on the abraded surface. This behavior indicates a self-healing capability. The results of micro-scratch tests indicated that the in-situ formed multiple oxide layers exhibited high adhesion strength in the shear direction after the 2000 h corrosion test.