IR Mechanism of Crevice Corrosion for Alloy T-2205 Duplex Stainless Steel in Acidic-Chloride Media

Al-Khamis, Jamal N.; Pickering, H. W.

doi:10.1149/1.1380673

Cited by 30 publications

(42 citation statements)

References 27 publications

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“…5 The IR drop mechanism itself is not discussed further here, for numerous papers deal with this theory. [5][6][7][8][9][10][11][12] In this paper, the emphasis is placed on an experiment, and supporting calculations, to verify the critical crevice corrosion diagram for mild steel (MS) in an aqueous sodium acetateacetic acid (NaAc-AcH) buffer solution under anodic polarization conditions. Such a critical crevice corrosion diagram is based on the critical characteristic dimension, which marks the limit between crevices that show or do not show crevice corrosion.…”

Section: Ir Dropmentioning

confidence: 99%

Critical Characteristic Dimension or Geometry for Determining the Susceptibility of a Crevice to Crevice Corrosion

Vankeerberghen¹

2004

CORROSION

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Crevices are invariably present in engineering structures. Hence, it is of interest to develop the ability to predict which geometries will, or will not, lead to crevice corrosion. Since many crevice corrosion theories have been proposed that depend on the material-environment combination, two systems have been selected for study: mild steel (MS) under anodic polarization in a sodium acetate-acetic acid buffer solution (NaAc-AcH) and Al in a sodium chloride (NaCl) solution. The onset of crevice corrosion is respectively believed to be determined by a critical potential drop (IR drop theory for MS in NaAc-AcH) and a critical species' concentration (critical crevice composition theory for Al in NaCl). In both cases, these critical values can be translated, by computation, into a critical characteristic crevice dimension determining the onset of crevice corrosion in one-dimensional crevices. The critical characteristic dimension marks the limit between crevices that show or do not show crevice corrosion. The calculations for the system where the critical crevice composition theory is operative have been performed with a fi nite element code to describe the mass transport of the various species involved. This approach allows the criterion (critical potential drop or critical crevice composition) to be evaluated for crevices of any geometry in real components.

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Section: Ir Dropmentioning

confidence: 99%

Critical Characteristic Dimension or Geometry for Determining the Susceptibility of a Crevice to Crevice Corrosion

Vankeerberghen¹

2004

CORROSION

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“…In the IR drop model, [4][5][6][7][8][9][10][11][12][13] crevice corrosion starts when the potential difference between the outside and the inside of the crevice becomes large enough to cause the transition from passive to active inside the crevice. The IR (ohmic potential) drop arises from the anodic current (I) from the inside to the outside of the crevice and the electric resistance (R) of the crevice solution and corrosion products.…”

mentioning

confidence: 99%

Visualization of pH and pCl Distributions: Initiation and Propagation Criteria for Crevice Corrosion of Stainless Steel

Kaji

Sekiai

Muto

et al. 2012

J. Electrochem. Soc.

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Both pH and pCl sensing plates were fabricated, and the H + and Cl − distributions in the crevice solution for 18Cr-10Ni-5.5Mn stainless steel were visualized at 0.3 V (vs. Ag/AgCl, 3.33 M KCl) in 0.01 M NaCl (pH 3.0, adjusted with H 2 SO 4 ) at 298 K. While the pH inside the crevice gradually decreased with time, no accumulation of Cl − ions occurred. The SO 4 2− ions that were added to adjust the pH probably accumulated to maintain electroneutrality. When the pH reached 1.7, a metastable pit was generated inside the crevice, providing a sharp decrease in pH to 0.4 and an increase in Cl − concentration to above 4 M. After that, the corroded area grew steadily with time, and the pH and the Cl − concentration remained constant at pH 0.4 and above 4 M Cl − . Acidification from pH 1.7 to 0.4 was induced by the hydrolysis of the dissolving metal ions from the pit and resulted in the depassivation of the surrounding steel matrix. The metastable pitting also caused the Cl − accumulation inside the crevice by electromigration. The crevice corrosion was found to be initiated when the pH and Cl − concentration inside the crevice reached the conditions for metastable pit formation.Crevice corrosion of stainless steels is a problem in chemical industries and marine structures, and it has been the subject of many investigations largely because crevice corrosion sometimes happens in steels that generally exhibit excellent corrosion resistance. 1 The prevention of crevice corrosion requires an in-depth understanding of its initiation process. In crevice corrosion, geometric restrictions cause deoxygenation inside the crevice, resulting in the separation of anodic and cathodic sites. On the anodic site (inside the crevice), metal ions accumulate by passive dissolution, which cause acidification of the crevice solution by hydrolysis. 2 The electromigration and accumulation of Cl − ions also occur inside the crevice. In the incubation time to crevice corrosion, the pH and the Cl − concentration of the crevice solution gradually reach the critical values for depassivation, and then the transition from passive to active dissolution occurs. This is the classical initiation mechanism (passive dissolution model) of crevice corrosion. 2 However, this mechanism appears not to be consistent with experimental observations. 2,3 The IR drop and metastable pitting models have been proposed for the initiation of crevice corrosion.In the IR drop model, 4-13 crevice corrosion starts when the potential difference between the outside and the inside of the crevice becomes large enough to cause the transition from passive to active inside the crevice. The IR (ohmic potential) drop arises from the anodic current (I) from the inside to the outside of the crevice and the electric resistance (R) of the crevice solution and corrosion products. In this model, acidification and Cl − accumulation bring about an active loop in the polarization curve in the crevice solutions, and both factors also accelerate the active dissolution rate. 13 Metastable (micro)...

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“…Following are the results for aluminum 6XXX; results for alloy T-2205 duplex stainless steel can be found elsewhere. 9,10 To provide the types of experimental data mentioned previously, an alloy/ electrolyte system's polarization curve must contain a large active peak and relatively low passive current. Then, crevice corrosion will immediately occur in a crevice of small AR that can be readily constructed in the laboratory with a relatively large opening/gap dimension (e.g., a = 0.05 cm).…”

Section: Crevice Corrosion In Aluminum 6xxx Alloysmentioning

confidence: 99%

“…During IR-induced crevice and pitting corrosion, large E(x) profiles on the crevice walls are also routinely measured using a microprobe reference electrode. [4][5][6][7][8][9][10][11] These same features of IR-induced crevice corrosion can also exist inside pits, stabilize their growth, 11 and even be responsible for the transition from metastable to stable pit formation. 6 The location of x pass on the crevice wall is observed to move towards the crevice mouth during crevice corrosion, a consequence of an increasing dE(x)/dx with time since the ionic current, I, increases with time as the exposed wall area increases over the geometrical wall area.…”

Section: Crevice Corrosion In Aluminum 6xxx Alloysmentioning

confidence: 99%

“…6 The location of x pass on the crevice wall is observed to move towards the crevice mouth during crevice corrosion, a consequence of an increasing dE(x)/dx with time since the ionic current, I, increases with time as the exposed wall area increases over the geometrical wall area. [4][5][6][7][8][9][10] Hence, the penetration profile on the crevice wall extends over more of the crevice wall with time of stable crevice corrosion. This motion of x pass , as well as the wall locations of the peak currents, to smaller x values with time as shown in Figure C, tends to extend the penetration profile toward the mouth (x = 0) of the crevice and to suppress the large variations of the current density in the active peak of the polarization curve.…”

Section: Crevice Corrosion In Aluminum 6xxx Alloysmentioning

confidence: 99%

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The localized corrosion of Al 6XXX alloys

Shaw¹,

McCosby²,

Abdullah

et al. 2001

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IR Mechanism of Crevice Corrosion for Alloy T-2205 Duplex Stainless Steel in Acidic-Chloride Media

Cited by 30 publications

References 27 publications

Critical Characteristic Dimension or Geometry for Determining the Susceptibility of a Crevice to Crevice Corrosion

Critical Characteristic Dimension or Geometry for Determining the Susceptibility of a Crevice to Crevice Corrosion

Visualization of pH and pCl Distributions: Initiation and Propagation Criteria for Crevice Corrosion of Stainless Steel

The localized corrosion of Al 6XXX alloys

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