Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2018)

For FY18, Savannah River National Laboratory (SRNL) focused on four main tasks in its study of corrosion of Hanford Double-Shell Tanks (DSTs). The New Limits task focused on the development of a pitting factor as a localized corrosion predictor. Electrochemical experiments were directed towards pitting factors between 1 and 2 (i.e., borderline conditions) and separating the effects of chloride and fluoride in the pitting factor equation. In addition, long term immersion testing experiments with partial and completely immersed coupons in solutions with a wide range of pitting factors were tested. Secondary liner studies continued this year with a new vapor corrosion inhibition (VCI) strategy in which ground water (GW) simulants at a specified concentration of commercial VCI were mixed. The specific concentrations were recommended by Cortec® and was compared with similar concentration of GW with calcium carbonate. The anodic drift task utilized a simulant corresponding to AN-107 waste tank chemistry. The chemistry was studied with three different surface conditions: mill-scale, partial mill-scale and ground to 600 grit to study the impact of different surfaces on the potential drift. The final task was focused on ammonia concentration determination of a vapor space corrosion (VSC) test vessel using Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) detector. A summary of each task is presented below.