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Title: MODELING THE CATHODIC REGION IN CREVICE CORROSION UNDER A THIN ELECTROLYTE FILM INCLUDING PARTICULATES

Abstract

Crevice corrosion may be limited by the capacity of the external cathodic region to support anodic dissolution currents within the crevice. The analysis here focuses on behavior of metal surfaces covered by a thin ({approx}microns) layer of the electrolyte film including particulates. The particulates can affect the cathode current capacity (I{sub total}) by increasing the solution resistance (''volume effect'') and by decreasing the electrode area (''surface effect''). In addition, there can be particulate effects on oxygen reduction kinetics and oxygen transport. This work simulates and characterizes the effect of a uniform particulate monolayer on the cathode current capacity for steady state conditions in the presence of a thin electrolyte film. Particulate configurations with varying particle size, shape, arrangement, volume fraction, and electrode area coverage were numerically modeled as a function of the properties of the system. It is observed that the effects of particles can be fully accounted for in terms of two corrections: the volume blockage effect on the electrolyte resistivity can be correlated using Bruggeman's equation, and the electrode coverage effect can be modeled in terms of a simple area correction to the kinetics expression. For the range of parameters analyzed, applying these two correction factors, cathodes coveredmore » with thin electrolyte films that contain particles can be represented in terms of equivalent homogeneous electrolytes that can then be analyzed using simpler approaches. Continuing work will examine the effects of greater volume fractions of particles and multiple particle layers.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
USDOE
OSTI Identifier:
884908
Report Number(s):
NA
MOL.20060406.0061, DC#46519; TRN: US200616%%315
DOE Contract Number:
NA
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CATHODES; CREVICE CORROSION; DISSOLUTION; ELECTROLYTES; KINETICS; OXYGEN; PARTICULATES; STEADY-STATE CONDITIONS; METALS; MATHEMATICAL MODELS

Citation Formats

A.S. Agarwal, U. Landau, X. Shan, and J.H. Payer. MODELING THE CATHODIC REGION IN CREVICE CORROSION UNDER A THIN ELECTROLYTE FILM INCLUDING PARTICULATES. United States: N. p., 2006. Web. doi:10.2172/884908.
A.S. Agarwal, U. Landau, X. Shan, & J.H. Payer. MODELING THE CATHODIC REGION IN CREVICE CORROSION UNDER A THIN ELECTROLYTE FILM INCLUDING PARTICULATES. United States. doi:10.2172/884908.
A.S. Agarwal, U. Landau, X. Shan, and J.H. Payer. Tue . "MODELING THE CATHODIC REGION IN CREVICE CORROSION UNDER A THIN ELECTROLYTE FILM INCLUDING PARTICULATES". United States. doi:10.2172/884908. https://www.osti.gov/servlets/purl/884908.
@article{osti_884908,
title = {MODELING THE CATHODIC REGION IN CREVICE CORROSION UNDER A THIN ELECTROLYTE FILM INCLUDING PARTICULATES},
author = {A.S. Agarwal and U. Landau and X. Shan and J.H. Payer},
abstractNote = {Crevice corrosion may be limited by the capacity of the external cathodic region to support anodic dissolution currents within the crevice. The analysis here focuses on behavior of metal surfaces covered by a thin ({approx}microns) layer of the electrolyte film including particulates. The particulates can affect the cathode current capacity (I{sub total}) by increasing the solution resistance (''volume effect'') and by decreasing the electrode area (''surface effect''). In addition, there can be particulate effects on oxygen reduction kinetics and oxygen transport. This work simulates and characterizes the effect of a uniform particulate monolayer on the cathode current capacity for steady state conditions in the presence of a thin electrolyte film. Particulate configurations with varying particle size, shape, arrangement, volume fraction, and electrode area coverage were numerically modeled as a function of the properties of the system. It is observed that the effects of particles can be fully accounted for in terms of two corrections: the volume blockage effect on the electrolyte resistivity can be correlated using Bruggeman's equation, and the electrode coverage effect can be modeled in terms of a simple area correction to the kinetics expression. For the range of parameters analyzed, applying these two correction factors, cathodes covered with thin electrolyte films that contain particles can be represented in terms of equivalent homogeneous electrolytes that can then be analyzed using simpler approaches. Continuing work will examine the effects of greater volume fractions of particles and multiple particle layers.},
doi = {10.2172/884908},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Mar 14 00:00:00 EST 2006},
month = {Tue Mar 14 00:00:00 EST 2006}
}

Technical Report:

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  • The present state of understanding of localized corrosion of passive metals is based primarily upon behavior under fully immersed solutions. There has been limited analysis of localized corrosion in moist layers of dust, particulate and deposits. This work as part of a multi-university Corrosion Cooperative of the DOE-OCRWM Science and Technology Program established to enhance the understanding of corrosion processes and materials performance. The objective of this project is to develop models to simulate localized corrosion. The present analysis focuses specifically on the cathodic region near a corrosion crevice with the objective of characterizing the effects of the critical processmore » parameters on the required current to sustain the crevice corrosion. Previous related analytical and numerical studies have focused on galvanic corrosion where the rates of the anodic and cathodic processes are comparable, analyzing mostly the effects of the electrode kinetics and the thickness of the electrolyte layer. A recent study considers the cathodic region for crevice corrosion. The work here determines two and three dimensional current and potential distributions over the cathode. The analyzed cathodic oxygen reduction region adjacent to the crevice is depicted in Fig. 1. This region is modeled for the presence of extremely thin (G{sub r} = 1-2000 {micro}m) electrolyte film. The electrolyte film may become discontinuous thus limiting the cathode behavior. Spatial variation of pH affecting the oxygen reduction kinetics, and oxygen diffusion limitations in the film are analyzed. Additionally, the presence of particulates is considered. The effects of macroscopic scale parameters, including the extent of the cathodic region (L = 0.1-30 mm), the crevice gap (G{sub a} = 1-25 {micro}m) and the film conductivity (0.012-1.2 mS/cm) on the current and potential distributions were modeled using an electrochemical CAD software. The total current which a specific cathode can provide to sustain the crevice corrosion, was calculated for limiting potential conditions (to prevent anode passivation) set at the crevice opening. Sample results are shown in Fig. 2. A range of electrode kinetics is explored including data typical to oxygen reduction kinetics on stainless-steel and on nickel based alloys. The time-dependent effects of the varying pH due to oxygen reduction were also simulated. The effect of solid particulate in the electrolyte layer was analyzed on both the macroscopic and microscopic level. The particulate effects on the current distribution were analyzed on the macroscopic scale applying Bruggeman's equation for average, ''effective'' properties, and on the microscopic scale, using detailed distributions around single particles and particle arrays. Experiments performed on cells emulating the simulated cathode region to validate the modeling data are reported. Both current distribution and changes in solution pH over the cathode were measured.« less
  • Crevice corrosion may initiate in confined regions due to transport limitations, followed by an accumulation of a highly corrosive chemistry, capable of dissolving the metal. The metal and the crevice former surface roughness, the presence of particulates under the crevice former and the accumulation of solid corrosion products at the corroding site would significantly affect the current and potential distribution at the anode by increasing the ohmic potential drop. Most crevice corrosion models focus on a smooth walled crevice of uniform gap and do not account for the changing profile after crevice corrosion has been initiated. In this work wemore » analyze the crevice (anodic) region and apply current and potential distribution models to examine the effects of the perturbed surface topography. The analysis focuses on three related issues: (1) the effects of surface roughness of the metal and the crevice former, (2) the effects of particulates under the crevice former, and (3) the evolution of the crevice profile with corrosion product accumulation at the active, anodic region.« less
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  • This report describes results achieved during phase 1 of a three-phase subcontract to develop and understand thin-film solar cell technology associated to CuInSe{sub 2} and related alloys, a-Si and its alloys, and CdTe. Modules based on all these thin films are promising candidates to meet DOE long-range efficiency, reliability, and manufacturing cost goals. The critical issues being addressed under this program are intended to provide the science and engineering basis for the development of viable commercial processes and to improve module performance. The generic research issues addressed are: (1) quantitative analysis of processing steps to provide information for efficient commercial-scalemore » equipment design and operation; (2) device characterization relating the device performance to materials properties and process conditions; (3) development of alloy materials with different bandgaps to allow improved device structures for stability and compatibility with module design; (4) development of improved window/heterojunction layers and contacts to improve device performance and reliability; and (5) evaluation of cell stability with respect to illumination, temperature, and ambient and with respect to device structure and module encapsulation.« less
  • This report describes the results achieved during Phase I of a three-phase subcontract to develop and understand thin-film solar cell technology associated with CuInSe2 and related alloys, a-Si and its alloys, and CdTe. Modules based on all these thin films are promising candidates to meet DOE long-range efficiency, reliability, and manufacturing cost goals. The critical issues being addressed under this program are intended to provide the science and engineering basis for developing viable commercial processes and to improve module performance. The generic research issues addressed are: (1) quantitative analysis of processing steps to provide information for efficient commercial-scale equipment designmore » and operation; (2) device characterization relating the device performance to materials properties and process conditions; (3) development of alloy materials with different bandgaps to allow improved device structures for stability and compatibility with module design; (4) development of improved window/heterojunction layers and contacts to improve device performance and reliability; and (5) evaluation of cell stability with respect to illumination, temperature, and ambient, and with respect to device structure and module encapsulation.« less