According to a recent study published in Corrosion
Science, scientists led by Prof. HUANG Qunying’s team from the Hefei Institutes of Physical Science of the
Chinese Academy of Sciences (CAS) have improved the corrosion resistance of
China low activation martensitic (CLAM) steel to lead-bismuth eutectic (LBE) by
applying cerium (Ce).
Lead-cooled fast reactor (LFR) with LBE is
expected to be widely used as the main coolant in many fields. However, LBE
corrosion, together with strong radiation and high temperature, can affect the
lifetime of LFR structural materials. Therefore, it is necessary to control the
dissolved oxygen concentration in LBE to improve its corrosion resistance.
CLAM steel is a candidate structural
material for LFR. Rare earth element Ce tends to segregate at grain boundary
and improve the stability of the grain boundary, so its application in steel
has been widely studied recent years. However, it is unclear whether it is
helpful to improve the LBE corrosion resistance of structural material.
In this study, the research team carried out
experimental studies on the corrosion behavior of CLAM and Ce-CLAM specimens in
an LBE environment with a dissolved oxygen concentration of 10-6 wt% at 500 ℃.
They found that Ce mainly existed at grain
boundaries, which effectively reduced the number of M23C6 and
the chromium (Cr)-poor area near grain boundaries, enhancing the stability of
grain boundaries.
With the increase of exposure time, the thickness of oxide scale on the surface
of the two specimens increased gradually. The growth rate constant kp of
oxide scale of Ce-CLAM was about half that of the scale in CLAM, indicating
that the addition of minor Ce improves the LBE corrosion resistance of CLAM
steel.
On this basis, a mechanism model of Ce
enhancing the corrosion resistance of CLAM steel in LBE was proposed.
The results provide experimental data and
theoretical reference for the optimal design of LBE corrosion resistance of
structural materials.