Stress Corrosion Cracking, Passive, and Localized Corrosion of Alloy 22 High-Level Radioactive Waste Containers

Abstract Tests were conducted to determine the passive corrosion rate, and the susceptibility of Alloy 22 to localized corrosion and stress corrosion cracking. The passive corrosion rate was found to be on the range of 10-9 to 10-7 A/cm2. The passive corrosion rate was not strongly dependent on either the solution pH in the range of 2.7 to 8.0 or chloride concentration from 0.028 to 4.0 M. Increasing the temperature from 25 to 95 °C resulted in an increase in the passive current density from 2 × 10-9 to 4 × 10-8 A/cm2. Results from repassivation potential measurements indicate that Alloy 22 was resistant to localized corrosion especially in solutions where the chloride concentration was less than 0.5 M. Similar results were obtained in stress corrosion cracking tests using fatigue precracked wedge loaded double cantilever beam specimens with an initial stress intensity of 34.8 MPa·m1/2. No stress corrosion cracking was observed after 8 months in 5 percent NaCl at 90 °C. Minor grain boundary attack and limited secondary cracking were observed after an 8 month exposure to 40 percent MgCl2 at 110 °C.