Temperature dependence of passivity degradation on UNS N08800 in near neutral crevice chemistries containing thiosulphate

Abstract Reduced sulphur induced corrosion of steam generator (SG) tubing in pressurized water reactor (PWR) is assumed to occur at low temperature. Corrosion of UNS N08800 in chloride and thiosulphate solutions at 20, 40 and 90 ℃ is systemically investigated by using polarization technique, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). It is concluded that thiosulphate can be reduced to S°, S 2 2− and S 2− , and incorporate into the passive film, which significantly depends on temperature. The evolution on pitting potentials in chloride + thiosulphate solution can be ascribed to the competitive adsorption of these two ions on the passive surface.