Abstract
In 2006, the Integrated Multi-function Corrosion Probe (IMCP), a new multi-function corrosion monitoring system, was designed for double-shell tank 241-AN-107 at the Department of Energy’s Hanford Site. As part of the design work, laboratory testing using the IMCP data collection hardware, software, electrodes, and non-radioactive 241-AN-107 waste simulant solutions was conducted to establish baseline IMCP corrosion monitoring instrumentation performance and to characterize data produced by the major modes of corrosion that could be expected in Tank 241-AN-107 supernate simulants, particularly those forms of corrosion that could initiate during off-normal or upset conditions such as pitting and/or stress corrosion cracking (SCC). Testing demonstrated that standard tank waste simulants produce low rates of uniform corrosion on tank steel as monitored with linear polarization resistance (LPR) and electrical resistance (ER) instrumentation. Additionally, as monitored with electrochemical noise (EN) instrumentation, uniform corrosion is characterized by random fluctuations of electrochemical current noise (ECN) and electrochemical potential noise (EPN) and low Pitting Percentage and Instability values (statistical parameters related to the degree of localized corrosion); pitting corrosion is characterized by the formation of numerous, distinct, relatively short-lived ECN and EPN transients over time, and moderately elevated Pitting Percentage and Instability values; and stress corrosion cracking (SCC), during active crack propagation, is characterized by negative mean current levels punctuated by occasional large, long-lived ECN and EPN transients. During SCC, the Pitting Percentage and Instability values are also highly elevated.
