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

摘要

The susceptibility of mill-annealed (MA) and gas tungsten arc welded (GTAW) Alloy 22 to Pb-assisted stress corrosion cracking (PbSCC) was evaluated in supersaturated PbCl_2 and Pb(NO_3)_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(NO_3)_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 PbCl_2 solutions. Constant deformation SCC tests indicate that MA and GTAW Alloy 22 were resistant to PbSCC in supersaturated PbCl_2 (16,000ppm Pb, 95℃, pH 0.5, and E_(applied) = -100, -50, 0, and 50mV_(SCE)) and Pb(NO_3)_2 (16,000ppm Pb, 95℃, pH 3.9 and 10.7 and E_(applied) = 50 and 140mV_(SCE), respectively). The overall results from this PbSCC investigation suggest that MA and GTAW Alloy 22 are resistant to SCC in supersaturated PbCl_2 and Pb(NO_3)_2 solutions at 95℃. 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.