Chemistry Envelope for Pitting and Stress Corrosion Cracking Mitigation

Wiersma, Bruce J.; Fuentes, Roderick E.; Stock, Leon M.

doi:10.2172/1568783

Cited by 10 publications

(26 citation statements)

References 4 publications

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“…Additionally, for dilute solutions, a minimum nitrite concentration of 0.2 M was required. A complete summary of the PF equation rationale and implementation was summarized in a recent report [8].…”

Section: Equationmentioning

confidence: 99%

“…For FY19, the PF equation was addressed for elevated temperatures and for other conditions to continue validating the equation as a satisfactory metric to determine pitting corrosion susceptibility over a more complete range of potential exposure conditions. More information of the New Limits Testing and how it is being recommended to be used for updating the waste chemistry limits, as well as a summary of all the testing performed can be found in a recent report by Wiersma et al [8].…”

Section: New Limits Pitting Corrosion Testingmentioning

confidence: 99%

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Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

Fuentes

Shukla

Crossland

et al. 2020

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VCIs formulations were added during mid-course of experiments, i.e., after coupons have experienced corrosion in the untreated GW simulant. Three tests were conducted using VCI-A and VCI-B. The first two tests were conducted using 100% recommended dosages of VCI-A and VCI-B. The third test was conducted at 10% of the recommended dosage of VCI-B. Following conclusions are made from the experimental data and results:  The corrosion rate data indicated that 10% of the recommended dosage is insufficient in mitigating corrosion. This observation is consistent with a prior study which also concluded that VCIs' effectiveness vanishes at 10% of the recommended dosages for the aboveground tank bottom underside application.  The data also showed that 100% recommended dosages of VCI-A and VCI-B mitigated pitting corrosion of weathered coupons. Specifically, VCI-A mitigated pitting corrosion in immersed, Level 2, and Level 3 coupons, whereas VCI-B mitigated pitting corrosion in immersed, Level 1, and Level 3 coupons. Statistical significance of corrosion rate decrease in Level 1 coupons for 100% recommended dosage of VCI-A and Level 2 coupons for 100% recommended dosage of VCI-B could not be established; this may be due to choice of coupons' surface orientation being vertical during the tests, leading to limited and uneven weathering during groundwater only and groundwater plus VCI exposures. 3. Long term OCP Drift Tests OCPs of carbon steel were measured in three simulants from the new limits testing. Two sets of coupons, with three coupons in each set, were fabricated with differing surface conditions. The coupons' surface conditions included a 600-grit polished surface, and a surface with mill-scale plus corrosion products from legacy carbon steel (rail car steel AAR TC-128). Two coupons, one coupon from each set, were placed in each chemistry, and OCPs of the coupons were monitored for five months. OCPs of the coupons with polished surfaces evolved in the anodic direction with respect to the initial values, whereas OCPs of two of the three coupons with mill-scale plus corrosion products evolved in cathodic direction with respect to the initial values. Terminal OCP of one mill-scale plus corrosion products coupon was about 100 mV anodic with respect to the initial value. CPP data of the polished coupons before OCP evolutions showed mixed responses, i.e., a clear delineation between pitting and no-pitting cannot be made, and CPP data after OCP evolutions remained mixed (category 3), indicating that change in OCP values did not affect the CPP responses. Following exposures of the coupons during OCP evolutions, CPP data for the mill-scale plus corrosion products coupons in the three simulants showed negative hysteresis (category 1), which is a sign of no-pitting. The OCP and CPP data indicate that simulant chemistry and surface condition affect extent and direction of OCP evolution, however, OCP evolution does not affect the pitting susceptibility. Electrochemical Impedance Spectroscopy (EIS) spectra of the polished coupon...

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Section: Equationmentioning

confidence: 99%

Section: New Limits Pitting Corrosion Testingmentioning

confidence: 99%

Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

Fuentes

Shukla

Crossland

et al. 2020

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“…The equation was validated with model simulations and comparison with historical results. The results were compiled in a report that is currently in draft form to be submitted to WRPS [20] summarizing the technical basis for the recommended changes in the chemistry controls.…”

Section: Equationmentioning

confidence: 99%

“…Several prior studies have been reported with same type of carbon-steel in the high-level waste simulant environments which are comparable to these simulant chemistries. OCPs of U-bend coupons were recorded before measuring SCC susceptibility of the material [20], [22]. The OCP data was collected at 50 °C and is listed in Table 5-11.…”

Section: Anodic Drift Studiesmentioning

confidence: 99%

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

Fuentes

Shukla

Peters

et al. 2019

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Corrosion Evaluation for Tank 241-AP-106 Re-purposing

Wiersma

2019

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Tank AP-106 will be an integral part of the Direct Feed Low Activity Waste (DF-LAW) activity. This tank is an underground, carbon steel, double shell tank (DST). Before it can be utilized, the Cs-137 concentration levels in the waste must be reduced significantly. The AP-106 re-purposing process will manage normal waste tank additions procedures such that waste acceptance criteria objectives for Cs-137 removal are achieved. As this process was being developed, concerns regarding tank integrity during and after the process to Tank AP-106 and associated tanks (i.e., AP-102, AN-101, and AP-108) were addressed. The degradation mechanisms identified include: general and pitting corrosion, caustic stress corrosion cracking, galvanic corrosion, and microbiologically induced corrosion (MIC). Recommendations were provided to minimize the exposure of the tank to corrosive conditions (see Section 6.0). These recommendations included chemistry adjustments at defined steps in the process that will maintain the waste in compliance with the corrosion control program. Additionally, sampling and inspection (see Sections 6.0 and 7.0, respectively) recommendations that will assess the final condition of the tank environment and the tank were presented. The greatest risk for this process involves the handling of large quantities of Columbia River water (i.e., greater than 450,000 gallons) within the AP-106, associated tanks and supporting infrastructure (i.e., transfer line piping). As long as this water is blended into the supernate in a timely fashion, and the waste is adjusted appropriately with corrosion inhibitors, the final condition is expected to be within compliance. Recommendations were also made to address process interruptions that could result in exposure of the tank walls to aggressive conditions.

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Chemistry Envelope for Pitting and Stress Corrosion Cracking Mitigation

Cited by 10 publications

References 4 publications

Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

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

Corrosion Evaluation for Tank 241-AP-106 Re-purposing

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