Corrosion of Alloy 600 by Cationic Resin Beads

Abstract

Several instances of corrosion and stress corrosion cracking in light water reactor coolants have been attributed to the incidental presence of ion exchange resin in the coolant. Tests performed in high temperature water slurries of cation exchange resins have shown preferential pitting and general attack of Alloy 600. Continuous ac impedance measurements were performed to monitor the corrosion during the test. The frequency dependence of the ac impedance allows separation of the resistance of the corroding interface from the resistance of the slurry. The results have been shown that attack commences at relatively low temperatures near 80°C, increases with increasing temperature up to 289°C, and slows with decomposition of the resin held at 289°C. Postmortem analysis showed hemispherical pitting under partially decomposed beads, surrounded by a scale enriched in chromium and sulfur.