A Comparison of the Passive Oxide Films Formed on CANDU Steam Generator Tubing Alloy 600 and Alloy 800

Abstract

Alloy 600 (A600) steam generator (SG) tubing has been shown to be susceptible to stress corrosion cracking (SCC). Alloy 800 (A800) was developed as a replacement, though it has shown susceptibility to corrosion under certain conditions. The properties of the passive oxide films on both alloys were extensively analyzed to determine why the performance of A800 is superior to that of A600. Surface analysis to determine oxide composition was performed using X-ray photoelectron spectroscopy (XPS) and Auger Electron spectroscopy (AES). Electrochemical measurements were made using anodic polarization and electrochemical impedance spectroscopy (EIS). The oxide films on A600 and A800 were shown to have different electrochemical and compositional properties.