Flow-assisted corrosion (FAC) is most frequently observed in regions of high disturbed cooling water flow during the operation of boiling water reactor (BWR) under hydrogen water chemistry (HWC). Carbon steels are extensively used in nuclear power plants and FAC of carbon steel in wet steam is known to be a major failure problem.

 GE developed noble metal technology as a new tool to mitigate the intergranular stress corrosion cracking (IGSCC) of BWR components. This approach involves improving the surface catalytic property and hence achieving the thermodynamically lowest corrosion potential (-500 mVshe) in the presence of stoichiometric excess hydrogen. In addition, Zinc oxide (ZnO) has been added into the BWR feedwater because of the beneficial implication in reducing buildup of radioactive species in the oxide film.

 It was shown that the noble metal on the surface shifted the ECP to the noble direction in reducing environments at low oxygen concentrations by catalyzing the hydrogen/oxygen water reduction reaction and hence decreased the flow-assisted corrosion rate (or erosion corrosion rate) of carbon steel. Furthermore, Zn was incorporated into the oxide layer and increased the FAC resistance.

Electrochemical and surface analysis on the role of noble metal and Zn additives in high temperature water will be described in detail.