The Effect of Environmental Chemistry on the Pb Assisted Stress Corrosion Cracking Susceptibility of Mill-Annealed Alloy 22 and GTAW Weldments

Abstract

ABSTRACTThe susceptibility of mill-annealed (MA) and gas tungsten arc welded (GTAW) Alloy 22 to Pb-assisted stress corrosion cracking (PbSCC) was evaluated in supersaturated PbCl2 and Pb(NO3)2 solutions. The solution chemistries and pH were varied to evaluate the effects of specific Pb-bearing species on the SCC resistance of GTAW Alloy 22 double U-bend samples. Anodic polarization tests in acidic and basic supersaturated Pb(NO3)2 solutions indicated that the passive current densities generally increased with applied potential. These results were then compared to previous anodic polarizations results for supersaturated acidic PbCl2 solutions. Constant deformation SCC tests indicate that MA and GTAW Alloy 22 were resistant to PbSCC in supersaturated PbCl2 (16,000ppm Pb, 95°C, pH 0.5, and Eapplied = -100, -50, 0, and 50mVSCE) and Pb(NO3)2 (16,000ppm Pb, 95°C, pH 3.9 and 10.7 and Eapplied = 50 and 140mVSCE, respectively). The overall results from this PbSCC investigation suggest that MA and GTAW Alloy 22 are resistant to SCC in supersaturated PbCl2 and Pb(NO3)2 solutions at 95°C. Provided that these high Pb concentrations are not attainable in the anticipated repository environments, Alloy 22 is unlikely to be susceptible to SCC by the presence of Pb.