Abstract
Corrosion in the vapor space and at the liquid/air interface of the Department of Energy (DOE) high level waste (HLW) tanks have emerged as potentially active corrosion mechanisms. Controls on the solution chemistry are in place to preclude the initiation and propagation of further nitrate induced pitting and stress corrosion cracking. However, recent experience has shown that steel not in contact with the bulk waste solution but exposed to the “vapor space” above the bulk waste and the liquid/air interface may be vulnerable to pitting or stress corrosion cracking. Experimentation was performed to determine the influence of steel surface characteristics and solution chemistry on pitting rates within the vapor space and at the liquid/air interface on ASTM A537 steels, the materials of construction of the tanks. The results suggest that inhibited bulk solution chemistry does not ensure pitting protection within the vapor space when there are surface inhomogeneities. However, the characteristic residual salts on the steel play a key role in the pitting characteristics.
