The effect of surface property on the polarization behavior of hydrogen (H 2 ) oxidation, oxygen (O 2 ) reduction, and electrochemical corrosion potential (ECP) on Type 304 stainless steel (SS) in high temperature, high purity water was studied. It is evident that the presence of noble metals on the oxide surface dramatically improves the hydrogen oxidation kinetics and thus enhances the catalytic recombination efficiency of H2 to O2 to form H2O. The enhancement in the catalytic nature on 304 SS surface doped with noble metals results in a thermodynamically lowest electrochemical corrosion potential (ECP) value (<-500 mV vs. standard hydrogen electrode, SHE) when a stoichiometric or higher amount of hydrogen is present in the water. It is also observed that the insulated protective coating (IPC) layer created with a powder of yttria-stabilized zirconia (YSZ) by the thermal spray restricted the oxidant transport rate to the metal surface, and the ECP remained at <-500 mV(SHE) in 288 o C water without addition of hydrogen (H2).
Key Words: High temperature water, BWR, 304 SS, YSZ, noble metal, oxygen, hydrogen