Chloride Ion Penetration of Passive Films on Iron

Murphy, Oliver J.; Bockris, J. O'm.; Pou, Tong E.; Tongson, L. L.; Monkowski, M.D.

doi:10.1149/1.2120098

Cited by 35 publications

(22 citation statements)

References 4 publications

(5 reference statements)

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“…43 In this case, the effective surface area of the Fe(0) electrode would be larger than previously measured, thus decreasing the effective current density, and by eq 4, the anodic potential and likelihood for O 2 production would also decrease. Furthermore, Cl − is also recognized to dissolve or inhibit the formation of Fe (oxyhydr)oxide passive layers on Fe(0), 45 which would lead to a decrease in anodic interface potential, favoring a larger φ.…”

Section: Methodsmentioning

confidence: 99%

Production and Transformation of Mixed-Valent Nanoparticles Generated by Fe(0) Electrocoagulation

Dubrawski

Genuchten

Delaire

et al. 2015

Environ. Sci. Technol.

112

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Mixed-valent iron nanoparticles (NP) generated electrochemically by Fe(0) electrocoagulation (EC) show promise for on-demand industrial and drinking water treatment in engineered systems. This work applies multiple characterization techniques (in situ Raman spectroscopy, XRD, SEM, and cryo-TEM) to investigate the formation and persistence of magnetite and green rust (GR) NP phases produced via the Fe(0) EC process. Current density and background electrolyte composition were examined in a controlled anaerobic system to determine the initial Fe phases generated as well as transformation products with aging. Fe phases were characterized in an aerobic EC system with both simple model electrolytes and real groundwater to investigate the formation and aging of Fe phases produced in a system representing treatment of arsenic-contaminated ground waters in South Asia. Two central pathways for magnetite production via Fe(0) EC were identified: (i) as a primary product (formation within seconds when DO absent, no intermediates detected) and (ii) as a transformation product of GR (from minutes to days depending on pH, electrolyte composition, and aging conditions). This study provides a better understanding of the formation conditions of magnetite, GR, and ferric (oxyhydr)oxides in Fe EC, which is essential for process optimization for varying source waters.

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Section: Methodsmentioning

confidence: 99%

Production and Transformation of Mixed-Valent Nanoparticles Generated by Fe(0) Electrocoagulation

Dubrawski

Genuchten

Delaire

et al. 2015

Environ. Sci. Technol.

112

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“…In the meanwhile, chloride-induced modification to the film has to be experimentally addressed as well. It is worthy of note that these issues were extensively studied by X-ray photoelectron spectroscopy (XPS) 7 , 14 – 21 , Auger electron spectroscopy (AES) 7 , 14 , 16 , 19 , 22 – 27 , secondary ion mass spectrometry 7 , 8 , 16 , 19 , 25 , and radiotracer techniques 11 . Nonetheless, it is still very difficult and challenging to guarantee the precision and accuracy of observed locations and concentrations of a very small amount of chloride in an extremely thin passive film with a thickness of only a few nanometers.…”

Section: Introductionmentioning

confidence: 99%

“…Nonetheless, it is still very difficult and challenging to guarantee the precision and accuracy of observed locations and concentrations of a very small amount of chloride in an extremely thin passive film with a thickness of only a few nanometers. Much of evidence on the incorporation of Cl − in the passive oxide film can be mainly classified into two groups: one is chloride incorporation 7 , 8 , 11 , 14 – 17 , 22 – 24 , and the other is chloride absence in the passive film 14 , 18 – 21 , 25 – 27 . In the case of incorporation, the location of chloride in the passive film is also controversy.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of incorporation, the location of chloride in the passive film is also controversy. Some investigators declare that Cl − locate or concentrate in the outer layer of the film 7 , 14 – 16 , 22 , 23 , whereas some others claim it is in the inner layer 8 , 24 . In reality, most of the reported methods do not directly identify the presence of chloride or its location within the passive film.…”

Section: Introductionmentioning

confidence: 99%

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Unmasking chloride attack on the passive film of metals

et al. 2018

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Nanometer-thick passive films on metals usually impart remarkable resistance to general corrosion but are susceptible to localized attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Over the past decades, several classic theories have been proposed and accepted, based on hypotheses and theoretical models, and oftentimes, not sufficiently nor directly corroborated by experimental evidence. Here we show experimental results on the structure of the passive film formed on a FeCr15Ni15 single crystal in chloride-free and chloride-containing media. We use aberration-corrected transmission electron microscopy to directly capture the chloride ion accumulation at the metal/film interface, lattice expansion on the metal side, undulations at the interface, and structural inhomogeneity on the film side, most of which had previously been rejected by existing models. This work unmasks, at the atomic scale, the mechanism of chloride-induced passivity breakdown that is known to occur in various metallic materials.

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“…The ability of the halides to cause the breakdown of passivity of iron is classically investigated through chronoamperometric measurements, where a constant electrical potential is applied, and by examining the aspect of the samples together with the results inferred from surface analytical techniques. However, it has to be noted that in these previous studies the halides were either pres-ent from the beginning in the passivating or buffer solution, or added into the used passivating solution, through a small volume of concentrated solution or as a solid content, once the passive film has been formed [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Within these conditions, it may be envisaged that the aggressiveness of the halides towards the passive film could be hampered and even altered by the anions coming from the buffer or passivating solution.…”

Section: Introductionmentioning

confidence: 99%

Implications of the kosmotrope/chaotrope nature of the anions on the breakdown of passivity of iron by halides

Trompette

2014

Corrosion Science

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The comparative aggressiveness of NaF and NaCl solutions on the breakdown of passivity of iron has been investigated once the passivating borate buffer solution has been removed. The results highlight the inhibitive action of borate anions towards the less aggressive kosmotrope fluorides. Without borates, the kinetics of attack by fluorides is slower as the prepassivation is longer, and it is considerably retarded when compared to the case with the chaotrope chlorides. The high positive viscosity B coefficient value of borate anion argues in favor of its use as an inhibitor or as an efficient electrolyte for anodization baths. 2. Material and methods The chemical compounds: sodium fluoride (NaF), sodium chloride (NaCl), sodium bromide (NaBr), sodium tetraborate decahydrate (Na 2 B 4 O 7 ,10H 2 O), boric acid (H 3 BO 3), were analytical grade products manufactured by Sigma-Aldrich (France). Deionized water was taken as a solvent for the preparation of the electrolyte solutions. The pH of the solutions was measured with an electronic pH-meter (Eutech Intruments). NaCl solution at 0.1 M concentration with a pH 10 was prepared by adding some droplets of a sodium hydroxide (NaOH) solution at 0.1 M concentration. Small iron plates were cut from a commercial Fe foil (99.99%, Goodfellow, UK) with a thickness of 0.25 mm to obtain rectangular shape (1.5 cm Â 0.5 cm). Before use, the plates were mechanically polished with 1200 grit SiC. Then they were washed in acetone and rinsed with deionized water.

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Chloride Ion Penetration of Passive Films on Iron

Abstract: Models of the passive layer on iron are of two kinds--hydrated amorphous (I) or anhydrous polycrystalline (2).

Cited by 35 publications

References 4 publications

Production and Transformation of Mixed-Valent Nanoparticles Generated by Fe(0) Electrocoagulation

Production and Transformation of Mixed-Valent Nanoparticles Generated by Fe(0) Electrocoagulation

Unmasking chloride attack on the passive film of metals

Implications of the kosmotrope/chaotrope nature of the anions on the breakdown of passivity of iron by halides

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