EVALUATION OF LABORATORY SCREENING TECHINIQUES FOR LIQUID AIR INTERFACE CORROSION IN HANFORD WASTE S

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Product Number: 51312-01562-SG

ISBN: 01562 2012 CP

Author: Hongbo Cong

Publication Date: 2012

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The leak integrity of the nuclear waste storage tanks at Hanford and Savannah River sites could be compromised by corrosion related phenomena. Corrosion at the liquid-air interface (LAI) was first observed on A537 carbon steel in nuclear waste simulants in the laboratory and this triggered a series of investigations in an attempt to identify the critical factors that initiate LAI corrosion. Although a clear understanding on the initiation mechanism is still lacking a reliable laboratory screening technique is highly desirable to distinguish the conditions that will initiate LAI corrosion from those that will not. Cyclic potentiodynamic polarization (CPP) experiments were performed using two types of electrode setups: (1) half-immersed specimens and (2) multiple crevice assembly (MCA). CPP experiments with half-immersed specimens offer a direct and intuitive observation of LAI corrosion. Previous testing program indicated the concurrence of LAI corrosion and unintended crevice corrosion. This suggests that the mechanisms of LAI corrosion and crevice corrosion may be similar where the LAI meniscus may possibly act like a restricted-access crevice. Therefore CPP experiments with an MCA were performed according to ASTM standard G192-08. These two setups were evaluated in a variety of nuclear waste simulants and the CPP results were compared with long term exposure experiments of half-immersed specimens under both polarized and freely corroding conditions.