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Title: Provide thermogravimetric analysis data to performance assessment

Abstract

Recent experimental testing has investigated the effect of a deposited mixed salt on the corrosion of carbon steel in high relative humidity air. This result is compared with previous studies where pure sodium chloride was deposited. There are aspects of the degradation process which are significantly different when the different salts are deposited. With deposited sodium chloride, corrosion occurs almost immediately after introduction of 80% RH air. With deposited mixed salts, there is an initial inhibition of corrosion in 80% RH air. After the initial inhibition period, corrosion occurs at localized regions of the specimen. At longer times, the specimen suffers extensive corrosion. A very porous and non-adherent corrosion product forms and readily spalls. The initial inhibition of the corrosion with the deposited mixed salt is most likely due to the bicarbonate component. Bicarbonate is a known inhibitor of general corrosion of carbon steel [Thomas, 1994] and a promoter of localized corrosion at moderate alkalinity when chloride ions are present [Marsh, 1985]. The results of this testing indicate that the bicarbonate component of thin water layers can initially inhibit corrosion of the carbon steel. With time, however, inhibition is lost. A mechanism for this loss of inhibition is suggested. Itmore » is plausible that moderately alkaline bicarbonate aqueous solutions could develop on the surface of a waste package due to Yucca Mountain water contacting the waste packages. Aqueous conditions might develop where carbon steel is susceptible to localized corrosion [Dunn, 1998]. The initial test results presented here suggest that the inhibition of general corrosion, and hence, the promotion of localized corrosion of carbon steel by thin aqueous bicarbonate-chloride layers may not be sustainable. Additional testing is underway to further understand the effects of thin aqueous solution chemistry on carbon steel corrosion.« less

Authors:
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (United States)
Sponsoring Org.:
USDOE Office of Civilian Radioactive Waste Management, Washington, DC (United States)
OSTI Identifier:
676812
Report Number(s):
UCRL-ID-129842
ON: DE98057736
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jan 1998
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 05 NUCLEAR FUELS; CORROSION; CARBON STEELS; SALTS; ACID CARBONATES; RADIOACTIVE WASTE STORAGE; CONTAINERS

Citation Formats

Gdowski, G. Provide thermogravimetric analysis data to performance assessment. United States: N. p., 1998. Web. doi:10.2172/676812.
Gdowski, G. Provide thermogravimetric analysis data to performance assessment. United States. doi:10.2172/676812.
Gdowski, G. Thu . "Provide thermogravimetric analysis data to performance assessment". United States. doi:10.2172/676812. https://www.osti.gov/servlets/purl/676812.
@article{osti_676812,
title = {Provide thermogravimetric analysis data to performance assessment},
author = {Gdowski, G},
abstractNote = {Recent experimental testing has investigated the effect of a deposited mixed salt on the corrosion of carbon steel in high relative humidity air. This result is compared with previous studies where pure sodium chloride was deposited. There are aspects of the degradation process which are significantly different when the different salts are deposited. With deposited sodium chloride, corrosion occurs almost immediately after introduction of 80% RH air. With deposited mixed salts, there is an initial inhibition of corrosion in 80% RH air. After the initial inhibition period, corrosion occurs at localized regions of the specimen. At longer times, the specimen suffers extensive corrosion. A very porous and non-adherent corrosion product forms and readily spalls. The initial inhibition of the corrosion with the deposited mixed salt is most likely due to the bicarbonate component. Bicarbonate is a known inhibitor of general corrosion of carbon steel [Thomas, 1994] and a promoter of localized corrosion at moderate alkalinity when chloride ions are present [Marsh, 1985]. The results of this testing indicate that the bicarbonate component of thin water layers can initially inhibit corrosion of the carbon steel. With time, however, inhibition is lost. A mechanism for this loss of inhibition is suggested. It is plausible that moderately alkaline bicarbonate aqueous solutions could develop on the surface of a waste package due to Yucca Mountain water contacting the waste packages. Aqueous conditions might develop where carbon steel is susceptible to localized corrosion [Dunn, 1998]. The initial test results presented here suggest that the inhibition of general corrosion, and hence, the promotion of localized corrosion of carbon steel by thin aqueous bicarbonate-chloride layers may not be sustainable. Additional testing is underway to further understand the effects of thin aqueous solution chemistry on carbon steel corrosion.},
doi = {10.2172/676812},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1998},
month = {1}
}