Effect of Simulated Groundwater Chemistry on Stress Corrosion Cracking of Alloy 22

Abstract Slow strain rate tests were performed to evaluate the effect of simulated groundwater chemistry variations on the stress corrosion cracking (SCC) susceptibility of mill-annealed Alloy 22 (UNS N06022). Tests were conducted in which the constituent anionic species were removed selectively from simulated concentrated water (SCW). SCC was observed in SCW and its variations (removal of nitrate, sulfate, fluoride, or chloride) at a high anodic potential of 356 mV vs saturated calomel electrode (SCE) at 95°C (203°F). Although the bicarbonate ion is the predominant constituent in SCW causing SCC, a synergistic effect exists between the bicarbonate and chloride ions. At a constant bicarbonate concentration, the susceptibility of Alloy 22 to SCC increases with increasing chloride ion concentrations and decreases with temperature. In bicarbonate plus chloride solutions, SCC was only observed at high anodic potentials. No SCC was observed in sodium chloride plus sodium nitrate solutions in the absence of bic...