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Title: Modeling the Effects of Crevice Former, Particulates , and the Evolving Surface Profile in Crevice Corrosion

Abstract

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 we 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.

Authors:
; ; ;
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
USDOE
OSTI Identifier:
899321
Report Number(s):
NA
MOL.20070129.0227, DC# 49966; TRN: US200709%%447
DOE Contract Number:
NA
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CORROSION PRODUCTS; CREVICE CORROSION; PARTICULATES; ROUGHNESS; METALS; MATHEMATICAL MODELS

Citation Formats

A.S. Agarwal, U. Landau, X. Shan, and J.H. Payer. Modeling the Effects of Crevice Former, Particulates , and the Evolving Surface Profile in Crevice Corrosion. United States: N. p., 2006. Web. doi:10.2172/899321.
A.S. Agarwal, U. Landau, X. Shan, & J.H. Payer. Modeling the Effects of Crevice Former, Particulates , and the Evolving Surface Profile in Crevice Corrosion. United States. doi:10.2172/899321.
A.S. Agarwal, U. Landau, X. Shan, and J.H. Payer. Thu . "Modeling the Effects of Crevice Former, Particulates , and the Evolving Surface Profile in Crevice Corrosion". United States. doi:10.2172/899321. https://www.osti.gov/servlets/purl/899321.
@article{osti_899321,
title = {Modeling the Effects of Crevice Former, Particulates , and the Evolving Surface Profile in Crevice Corrosion},
author = {A.S. Agarwal and U. Landau and X. Shan and J.H. Payer},
abstractNote = {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 we 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.},
doi = {10.2172/899321},
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:

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  • Crevice corrosion is an important mode of localized corrosion to be evaluated for the long-term performance of corrosion resistant alloys in high temperature, aqueous environments. This work focuses on the evolution of corrosion damage of Ni-Cr-Mo alloys in hot brines. For the initiation of crevice corrosion, a critical crevice chemistry must develop within the crevice to break down the passive film. The geometry of the crevice and particularly the height of the crevice gap is an important parameter, with tighter crevices being more aggressive. Crevice corrosion models mostly define a smooth walled crevice of uniform gap and do not accountmore » for the changing profile after crevice corrosion has initiated. As a complement to the earlier models of the cathodic region, they focus here on 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 surface roughness of the metal and the crevice former, (2) the effects of particulate within the crevice, and (3) the evolution of the crevice profile in the active, anodic region.« less
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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
  • Iron K-absorption edge spectra were obtained from the passive films on iron for the dried films in air (ex situ) and for the films in the passivating solutions (in situ). The ex situ results demonstrate that, while the structures of the films are more disordered than the spinel-like iron oxides (e.g. lambda-Fe2O3)), they are nevertheless closely related to these crystalline oxides. The in situ data shows evidence of a quite different structure, which may be due to the accommodation of hydrogen containing species into the structure.
  • This document contains: Structural studies on passive films using surface EXAFS, EX-SITU and IN-SITU sample and detector chambers for the study of passive films using surface EXAFS, and Ellipsometric studies of chelating inhibitor effects on the cathodic delamination of an organic coating on iron.