skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Evaluation of an Oxide Layer on NI-CR-MO-W Alloy Using Electrochemical Impedance Spectroscopy and Surface Analysis

Abstract

High corrosion resistance under very aggressive conditions is a distinguishing property of Ni-Cr-Mo-W alloys. One such alloy, Alloy 22, is a candidate material for fabrication of the outer layer of high-level nuclear waste (HLNW) packages for the proposed HLNW repository at Yucca Mountain, Nevada, USA. We are using Electrochemical Impedance Spectroscopy (EIS), ex-situ X-Ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectroscopy (ToF SIMS) to characterize the electrochemical properties and composition of the protective oxide formed on Alloy 22 surfaces. These studies have been conducted at temperatures up to 90 C at potentials from -0.8 V to 0.8 V (vs. Ag/AgCl (sat'd KCl)) in deaerated 5 mol L{sup -1} NaCl solution. Using this combination of techniques, we can correlate the electrical (from EIS) and compositional properties (from XPS, ToF SIMS) of the oxide. At more negative potentials (-0.8 V to -0.4 V) the film exhibits a low charge transfer resistance and high capacitance, indicating the presence of a very defective film with a high concentration of electronic defects. The presence of additional elements in the equivalent circuit, corresponding to water reduction, supports this suggestion. At these potentials, surface analysis techniques show a thin oxide layer with amore » low concentration of Cr203. Increasing the potential (to between -0.2 and 0.2 V) leads to a major increase in overall interfacial resistance consistent with the formation of an oxide with a small concentration of electronic defects. At the same time, the surface analysis techniques show increases in the film thickness and the Cr{sub 2}O{sub 3} content. A further increase in potential to 0.8 V, in general, leads to a decrease in interfacial resistance throughout the film. When the Cr{sub 2}O{sub 3} barrier layer is degraded, then the higher oxidation states of Mo and W species (MO{sup VI}, W{sup VI}) increase in concentration and are stored in the outer part of the film (at temperatures up to 60 C). The storage of these high oxidation state ions generates a high interfacial capacitance. At high temperature (above 60 C), the XPS and EIS show that the high oxidation states of Mo and W are absent. We think this is because they dissolve from the oxide under those conditions.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
USDOE
OSTI Identifier:
899320
Report Number(s):
NA
MOL.20070129.0236, DC# 50015; TRN: US0702197
DOE Contract Number:
NA
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; ALLOYS; CAPACITANCE; CORROSION RESISTANCE; DEFECTS; EQUIVALENT CIRCUITS; FABRICATION; IMPEDANCE; MASS SPECTROSCOPY; OXIDES; RADIOACTIVE WASTES; SPECTROSCOPY; STORAGE; THICKNESS; VALENCE; X-RAY PHOTOELECTRON SPECTROSCOPY; YUCCA MOUNTAIN

Citation Formats

D. Zagidulin, P. Jakupi, J.J. Noel, and D.W. Shoesmith. Evaluation of an Oxide Layer on NI-CR-MO-W Alloy Using Electrochemical Impedance Spectroscopy and Surface Analysis. United States: N. p., 2006. Web. doi:10.2172/899320.
D. Zagidulin, P. Jakupi, J.J. Noel, & D.W. Shoesmith. Evaluation of an Oxide Layer on NI-CR-MO-W Alloy Using Electrochemical Impedance Spectroscopy and Surface Analysis. United States. doi:10.2172/899320.
D. Zagidulin, P. Jakupi, J.J. Noel, and D.W. Shoesmith. Thu . "Evaluation of an Oxide Layer on NI-CR-MO-W Alloy Using Electrochemical Impedance Spectroscopy and Surface Analysis". United States. doi:10.2172/899320. https://www.osti.gov/servlets/purl/899320.
@article{osti_899320,
title = {Evaluation of an Oxide Layer on NI-CR-MO-W Alloy Using Electrochemical Impedance Spectroscopy and Surface Analysis},
author = {D. Zagidulin and P. Jakupi and J.J. Noel and D.W. Shoesmith},
abstractNote = {High corrosion resistance under very aggressive conditions is a distinguishing property of Ni-Cr-Mo-W alloys. One such alloy, Alloy 22, is a candidate material for fabrication of the outer layer of high-level nuclear waste (HLNW) packages for the proposed HLNW repository at Yucca Mountain, Nevada, USA. We are using Electrochemical Impedance Spectroscopy (EIS), ex-situ X-Ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectroscopy (ToF SIMS) to characterize the electrochemical properties and composition of the protective oxide formed on Alloy 22 surfaces. These studies have been conducted at temperatures up to 90 C at potentials from -0.8 V to 0.8 V (vs. Ag/AgCl (sat'd KCl)) in deaerated 5 mol L{sup -1} NaCl solution. Using this combination of techniques, we can correlate the electrical (from EIS) and compositional properties (from XPS, ToF SIMS) of the oxide. At more negative potentials (-0.8 V to -0.4 V) the film exhibits a low charge transfer resistance and high capacitance, indicating the presence of a very defective film with a high concentration of electronic defects. The presence of additional elements in the equivalent circuit, corresponding to water reduction, supports this suggestion. At these potentials, surface analysis techniques show a thin oxide layer with a low concentration of Cr203. Increasing the potential (to between -0.2 and 0.2 V) leads to a major increase in overall interfacial resistance consistent with the formation of an oxide with a small concentration of electronic defects. At the same time, the surface analysis techniques show increases in the film thickness and the Cr{sub 2}O{sub 3} content. A further increase in potential to 0.8 V, in general, leads to a decrease in interfacial resistance throughout the film. When the Cr{sub 2}O{sub 3} barrier layer is degraded, then the higher oxidation states of Mo and W species (MO{sup VI}, W{sup VI}) increase in concentration and are stored in the outer part of the film (at temperatures up to 60 C). The storage of these high oxidation state ions generates a high interfacial capacitance. At high temperature (above 60 C), the XPS and EIS show that the high oxidation states of Mo and W are absent. We think this is because they dissolve from the oxide under those conditions.},
doi = {10.2172/899320},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Dec 21 00:00:00 EST 2006},
month = {Thu Dec 21 00:00:00 EST 2006}
}

Technical Report:

Save / Share:
  • Ni-Cr-Mo-W alloys (C-group alloys) are well known as materials with very high Corrosion resistance in very aggressive environments, an asset that has motivated the selection of Alloy 22 as a waste package material in the Yucca Mountain Project for the long-term geologic disposal of spent nuclear fuel and other high-level radioactive wastes. The aim of this project is to elucidate the corrosion performance of Alloy 22 under aggressive conditions and to provide a conceptual understanding and parameter data base that could act as a basis for modeling the corrosion performance of waste packages under Yucca Mountain conditions. A key issuemore » in any corrosion process is whether or not the kinetics of the cathodic reactions involved can support a damaging rate of anodic metal (alloy) dissolution. Under Yucca Mountain conditions the primary oxidant available to drive corrosion (most likely in the form of crevice, or under-deposit, corrosion) will be oxygen. Here, we present results on the kinetics of oxygen reduction at the Alloy 22/solution interface.« less
  • The objective of this study is to investigate the composition of corrosion products and the metal surface within a crevice after localized corrosion. The analysis provides insight into the propagation, stifling and arrest processes for crevice corrosion and is part of a program to analyze the evolution of localized corrosion damage over long periods of time, i.e. 10,000 years and longer. The approach is to force the initiation of crevice corrosion by applying anodic polarization to a multiple crevice assembly (MCA). Results are reported here for alloy C-22, a Ni-Cr-Mo alloy, exposed to a high temperature, concentrated chloride solution. Controlledmore » crevice corrosion tests were performed on C-22 under highly aggressive, accelerated condition, i.e. 4M NaCl, 100 C and anodic polarization to -0.15V-SCE. The crevice contacts were by either a polymer tape (PTFE) compressed by a ceramic former or by a polymer (PTFE) crevice former. Figure 1 shows the polarization current during a crevice corrosion test. After an incubation period, several initiation-stifle-arrest events were indicated. The low current at the end of the test indicated that the metal surface had repassivated.« less
  • Bent beam and self-stressed specimens have been employed and shown to give results consistent with other types of specimens as reported in the literature. All tests have been conducted in the standard NACE, H/sub 2/S environment for initial screening and then in a 20 percent NaCl modified NACE solution. Among the higher strength corrosion resistant alloys, K Monel at 135 ksi yield strength did not fail in either environment at temperatures up to 425/sup 0/F stressed at the yield strength. Age hardenable A286 failed at 325/sup 0/F when stressed to the 190 ksi yield strength, but did not fail whenmore » stressed to an overaged yield strength of 135 ksi. A new NiCoCrMo age hardenable alloy heat treated to 220 ksi yield strength and stressed to this value did not fail in either environment at temperatures up to 420/sup 0/F. Also, this material was substantially ''brighter'' after the tests than either the K-Monel or A286.« less
  • Ni-Mo alloys containing at least 26 wt.% Mo have a negligible corrosion rate in boiling 10% hydrochloric acid and are therefore used in corrosive environments. A series of commercial Ni-Mo alloys has been developed with subtle variations in chemical composition. These alloys usually contain {approximately} 28 wt.% Mo with additions of up to 5% Fe and Cr. A significant amount of research has been performed to understand the microstructure and properties of these alloys, although most of the effort has concentrated on the Ni-Mo binary system. In some alloys with low Fe and Cr contents, a severe embrittlement problem hasmore » been observed due to the formation of the Ni{sub 4}Mo (D1{sub a}-ordered) phase within the microstructure. This research focuses on a commercial alloy with nominal composition Ni-28% Mo-1.4% Fe-0.4% Cr-0.1% Mn-0.003 wt.% C. The material supplied was a heat treatment coupon which had been attached to a large vessel during fabrication. Assessment of the chemical analysis of the alloy suggested that detrimental phases could be present or might appear during subsequent repair work. Therefore, it was important to assess the microstructural condition of the vessel, and in particular the kinetics of precipitation of Ni{sub 4}Mo.« less
  • Investigations to develop an isotropically ductile high temperature eutectic alloy first focused on identifying the cubic (gamma + alpha) phase field and the cubic plus (gamma ( sigma) phase field within the quaternary systems, Ni-Cr-W-Al. Nickel alloys containing O-15 w/o W, 2 w/o Al, and nominally 40 w/o Cr were shown to consist of a nickel-rich lamellar solid solution matrix saturated with tungsten and chromium, and aligned chromium rich lamellae containing nickel-rich Widmanstatten precipitate. Alloys containing 18 w/o W however consisted of a nickel-rich lamellar matrix and aligned sigma phase, identified by X-ray diffraction as approximately Cr8Ni5W. The attainment ofmore » significant low temperature ductility was found to be limited by the low ductility of sigma phase as previously observed for all multicomponent Ni-Cr-W-Al and Ni-Co-Cr-W-Al alloys containing 18 w/o W. Directionally solidified alloys with fully aligned gamma + alpha and gamma + sigma microstructures exhibited respectively either insufficient values of strength or ductility compared with conventional superalloys to be worthy of further development in this program. To meet the program objectives, alloys derived from the Ni3Al-Mo (gamma' - alpha) eutectic identified by us previously were selected for further investigation and optimization. Aluminum modifications of the pseudo-binary eutectic, gamma' - alpha, yielded ductile/ductile, gamma'/gamma - alpha aligned composite microstructures. (GRA)« less