Electrochemical Properties of Oxide Films Formed on Cold Worked Alloy600 and Alloy690 in Simulated PWR Primary Water Environments

Abstract

Passive films formed on Alloy 600 and Alloy 690 in the simulated primary water of pressurized water reactor were characterized by photo electrochemical current response focusing on the influence of the dissolved hydrogen and cold working. Some specimens were also analyzed by X-ray photoelectron spectroscopy using the hard X-ray generated by SPring-8.
Passive films on both alloys consisted of the oxide layer of p-type semiconductor properties with band gap energy (E_b) of 3.5 eV and the hydroxide layer of n-type semiconductor with E_b of 2.3 eV. However, the content of Ni in the oxide layer which may induce p-type semiconductor property is negligible small. The passive films on Alloy 600 become thinner by dissolved hydrogen, and less protective by cold working. Whereas passive films on Alloy 690, which were more protective than that on Alloy 600, were rarely influenced by cold working and dissolved hydrogen.