Determination of Corrosion Inhibitor Criteria for Type III/IIIA Tanks During Salt Dissolution Operations Summary Document

摘要

Dissolution of salt from Type III/IIIA waste tanks at the Savannah River Site may create solutions with inhibitor concentrations below those currently required (0.6M OH sup - and 1.1M OH sup - + NO sub 2 sup -) per the Corrosion Control Program for high nitrate salt solutions (5.5 to 8.5M NO sub 3 sup -). An experimental program was conducted to evaluate the corrosion susceptibility of grade A537 carbon steel for waste simulants containing 4.5-8.5M NaNO sub 3 with maximum inhibitor concentrations of 0.6M NaOH and 0.2M NaNO(sub 2). These maximum inhibitor concentrations used in this program are at a reduced level from those currently required. Current requirements were initially established for the Types I, II and IV tanks made of A285 carbon steel. The experimental program involved corrosion testing to evaluate the pitting and stress corrosion stress corrosion cracking (SCC) susceptibility of the Type III/IIIA waste tank materials. The program was conducted in two phases; the results of the first phase were reported previously (WSRC-STI-2006-00029). In this second phase, the corrosion specimens were modified to represent the 'as-fabricated' condition of the tank wall, and included specimens with mill scale, ground welds and stress-relief heat treatments. The complete description of the corrosion testing and the results are reported herein.