General Corrosion and Passive Film Stability

PDF Version Also Available for Download.

Description

We have studied Alloy 22 corrosion and passive film stability in nitrogen-purged Na-K-Cl-NO{sub 3} brines having NO{sub 3}:Cl ratios of 7.4 at 160 C and NO{sub 3}:Cl ratios of 0.5 and 7.4 at 220 C in autoclave experiments under a slight pressure. The experiments were done to show the effect of high nitrate brines on the durability of the Alloy 22 outer barrier of the waste canisters. Ratios of NO{sub 3}:Cl used in this study were lower than expected ratios for the repository environment at these temperatures and atmospheric pressures (NO{sub 3}:Cl > 25), however they were thought to be ... continued below

Physical Description

PDF-file: 35 pages; size: 6.9 Mbytes

Creation Information

Dixit, S; Roberts, S; Evans, K; Wolery, T & Carroll, S November 29, 2005.

Context

This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this report can be viewed below.

Who

People and organizations associated with either the creation of this report or its content.

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this report. Follow the links below to find similar items on the Digital Library.

Description

We have studied Alloy 22 corrosion and passive film stability in nitrogen-purged Na-K-Cl-NO{sub 3} brines having NO{sub 3}:Cl ratios of 7.4 at 160 C and NO{sub 3}:Cl ratios of 0.5 and 7.4 at 220 C in autoclave experiments under a slight pressure. The experiments were done to show the effect of high nitrate brines on the durability of the Alloy 22 outer barrier of the waste canisters. Ratios of NO{sub 3}:Cl used in this study were lower than expected ratios for the repository environment at these temperatures and atmospheric pressures (NO{sub 3}:Cl > 25), however they were thought to be high enough to inhibit localized corrosion. Localized corrosion occurred on the liquid-immersed and vapor-exposed creviced specimens under all conditions studied. Crevice penetration depths were difficult to quantify due to the effects of deformation and surface deposits. Further characterization is needed to evaluate the extent of localized corrosion. The bulk of the surface precipitates were derived from the partial dissolution of ceramic crevice formers used in the study. At this time we do not know if the observed localized corrosion reflects the corrosiveness of Na-K-Cl-NO{sub 3} solutions at elevated temperature over nine months or if it was an artifact of the experimental protocol. Nor do we know if much more concentrated brines with higher NO{sub 3}:Cl ratios formed by dust deliquescence will initiate localized corrosion on Alloy 22 at 160 and 220 C. Our results are consistent with the conclusion that nitrate concentrations greater than 18.5 molal may be required to offset localized corrosion of Alloy 22 at 160 and 220 C. Stability of the passive film and general corrosion were evaluated on the liquid-immersed and vapor-exposed non-creviced specimens. Elemental depth profiles of the vapor-exposed specimens are consistent with the development of a protective Cr-rich oxide near the base metal. The combined passive film and alloy oxide of the immersed specimens was much thicker than for the vapor-exposed specimens. This may be attributed to the inability to transport reactants away from the surface with limited amount of fluid in the condensate compared to the large reservoir for the liquid-immersed specimens. Elemental depth profiles of the liquid-immersed specimens suggest that Cr(III) and Mo(II) in the passive film are oxidized to Cr(VI) and Mo(VI) and are dissolved in the high nitrate brines, because the alloy oxide layers were enriched with Ni relative to Cr and Mo in the base metal. An alumino-silicate-chloride precipitate was identified on specimens immersed in solutions with a NO{sub 3}:Cl ratio of 0.5 at 220 C. Further characterization is needed to identify all secondary phases. The inability to extract reliable rates from weight loss measurements suggests that other techniques are needed to evaluate long-term general corrosion of Alloy 22.

Physical Description

PDF-file: 35 pages; size: 6.9 Mbytes

Language

Item Type

Identifier

Unique identifying numbers for this report in the Digital Library or other systems.

  • Report No.: UCRL-TR-217393
  • Grant Number: W-7405-ENG-48
  • DOI: 10.2172/889973 | External Link
  • Office of Scientific & Technical Information Report Number: 889973
  • Archival Resource Key: ark:/67531/metadc873099

Collections

This report is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this report?

When

Dates and time periods associated with this report.

Creation Date

  • November 29, 2005

Added to The UNT Digital Library

  • Sept. 21, 2016, 2:29 a.m.

Description Last Updated

  • Nov. 28, 2016, 6:28 p.m.

Usage Statistics

When was this report last used?

Congratulations! It looks like you are the first person to view this item online.

Interact With This Report

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

Citations, Rights, Re-Use

Dixit, S; Roberts, S; Evans, K; Wolery, T & Carroll, S. General Corrosion and Passive Film Stability, report, November 29, 2005; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc873099/: accessed December 15, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.