Reaction morphologies developed by nickel aluminides in type II hot corrosion conditions: The effect of chromium

Gheno, Thomas; Azar, Maryam Zahiri; Heuer, A. H.; Gleeson, Brian

doi:10.1016/j.corsci.2015.08.029

Cited by 42 publications

(17 citation statements)

References 49 publications

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“…In contrast to iron and nickel, chromium remains mainly as a solid, porous chromium‐iron oxide scale beneath the initial surface and only small amounts of chromium precipitated as oxides in the deposit. This is in good agreement with Gheno et al, who estimated the solubility minimum of chromium oxide to be close to the present gas composition. They further explained that the predominant solute of the chromium oxide is the result of an alteration of the salt chemistry.…”

Section: Resultssupporting

confidence: 93%

“…Therefore, the acidic solubility also decreases towards the salt‐oxide interface and the negative solubility criterion is not satisfied. This is observed in the dissolution of pure metals when no new salt is supplied, whereas in the dissolution of iron‐, nickel‐, and cobalt‐based alloys a synergetic effect is proposed to fulfill this criterion . When two (or more) oxides are dissolved simultaneously, one could dissolve as an acidic solute by reacting with SO 3 , whereas the other could dissolve as a basic solute by reacting with Na 2 O.…”

Section: Introductionmentioning

confidence: 99%

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Hot corrosion Type II of FeCr‐based model alloys for boiler and heat exchanger applications

König

Montero

Galetz

2019

Materials & Corrosion

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The hot corrosion Type II of the alloys FeCr20, FeCr20Ni10, FeCr20Ni20, and FeCr20Co10 is investigated at 700°C in air + 0.5% SO2 with deposits consisting of Na2SO4 and a eutectic mixture of Na2SO4 and MgSO4 for 24, 100, and 300 h. The alloying elements nickel and cobalt have a positive influence when tests are conducted using a MgSO4‐Na2SO4 deposit. In this case, they reduce the metal loss and increase the time to the propagation stage. In contrast, when the alloys are exposed with a Na2SO4 deposit, these alloying elements increase the metal loss and allow for the transition to the propagation stage because they can form molten phases with the Na2SO4. During the incubation stage an oxide scale forms on the FeCr20 alloy, which is thicker than the one formed during exposure without a deposit, and iron oxides are observed, which precipitate in the deposit. The propagation stage occurs by a dissolution and precipitation mechanism forming localized pitting attack. Iron is the main species that dissolves and precipitates, while chromium remains mainly as an oxide beneath the initial surface. The additional elements are found in the pit and in the salt deposit.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Hot corrosion Type II of FeCr‐based model alloys for boiler and heat exchanger applications

König

Montero

Galetz

2019

Materials & Corrosion

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“…Features indicative of the proposed mechanisms in both studies were extensive sulfide formation below the deposit and the NiSO 4 –Na 2 SO 4 eutectic forming at the sulfate/oxide interface. In the case of nickel‐based alloys, Gheno et al proposed a mechanism of synergistic fluxing in which oxide‐scale dissolution is enhanced by the presence of multiple oxides. The concept of synergistic fluxing was first proposed by Hwang and Rapp …”

Section: Introductionmentioning

confidence: 99%

A new solid‐state mode of hot corrosion at temperatures below 700°C

Kistler

Chen

Meier

et al. 2019

Materials & Corrosion

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Preliminary results on a single‐crystal nickel‐based superalloy indicated that hot corrosion can occur at temperatures as low as 550°C, where liquid formation, generally believed to be responsible for Type II hot corrosion, is not predicted. Additional tests were conducted on pure‐nickel samples at 650°C and below to more clearly elucidate the mechanism of this very low‐temperature hot corrosion. Environments in dry air and O2‐(2.5, 10, 100, and 1000) ppm SO2 were studied. Based on the results obtained, a solid‐state corrosion mechanism was inferred. The mechanism relies on the formation of a previously unreported compound phase, which was identified using transmission electron microscope analysis that indicated the stoichiometry of Na2Ni2SO5. Furthermore, it was nanocrystalline in structure and metastable. It was deduced that the Na2Ni2SO5 formation was responsible for the rapid nickel transport required for the observed accelerated corrosion process. Moreover, its eventual decomposition resulted in a mixed product of porous NiO with embedded particles of Na2SO4. Application of the proposed mechanism to nickel‐based alloys is discussed.

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“…Nevertheless, the separation of substrate curves is higher in comparison with the other ones studied, reporting highest corrosion rates. On the other hand, the corrosion rate is very low for both systems (Three-layer Painting System and Thermal Spray System), generating a protection of zinc and aluminum pigments respectively; although there is a little consumption increase of current density in 2250 hours, for both systems, fact that raises zinc and aluminum consumption, forming oxides: The above phenomena are corroborated on the SEM images, leading to lose of paint adherence and an increment of rate corrosion [27][28][29][30][31][32][33].…”

Section: Figurementioning

confidence: 92%

Corrosion protection in saline environment of a carbon steel coated (aluminum & three-layer painting system) by eats

Pérez-Muñoz¹,

Marulanda-Arévalo²,

Téllez³

2018

Rev.Fac.Ing.Univ.Antioquia

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This paper presents a comparative study on corrosion protection of low-carbon steel coated with two different painting systems. The first set of samples was coated with an aluminum layer of primer deposited by Electric Arc Thermal Spray (EATS), after which two additional layers of paint were applied, thereby creating an aluminum-painting system; while the second set of samples was coated with the traditional three-layer painting system (zinc-rich layer of primer). Afterwards, all the samples were exposed to the salt spray chamber. The samples were monitored to record their reactions in the corrosive saline environment. Scanning Electron Microscopy (SEM), adhesion and electrochemical corrosion tests were performed to characterize the coatings and report changes in their properties (adhesion, topography and homogeneity), which are related to exposure time. The three-layer painting system barely complied with manufacturer claims on protection time under corrosive conditions; on the other hand, the aluminum-painting system yielded better results by prolonging protection time. RESUMEN: Este artículo presenta un estudio comparativo de protección contra la corrosión de aceros de bajo carbono recubiertos con dos sistemas diferentes de pintura. El primer grupo de muestras fue recubierto con una capa de aluminio depositada por Rociado Térmico por Arco Eléctrico (EATS por sus siglas en inglés), subsecuentemente dos capas adicionales de pintura fueron aplicadas, creando así un sistema aluminio/pintura. Mientras que, un sistema tradicional de tres capas de pintura (primera capa de pintura rica en zinc) fue depositado en el segundo grupo de muestras. Finalmente, todas las muestras fueron expuestas en la cámara de niebla salina. Las muestras fueron monitoreadas para obtener su comportamiento en el corrosivo ambiente salino. Microscopia Electrónica de Barrido (SEM por sus siglas en inglés), ensayos de adhesión y corrosión electroquímica fueron realizadas para caracterizar los recubrimientos y reportar los cambios en sus propiedades (adhesión, topografía y homogeneidad), las cuales están relacionadas con el tiempo de exposición. El sistema de tres capas escasamente cumplió con la garantía dada por su fabricante en lo referente al tiempo de protección bajo condiciones corrosivas; por otro lado, el sistema de aluminio/pintura entregó mejores resultados al prolongar el tiempo de protección.

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Reaction morphologies developed by nickel aluminides in type II hot corrosion conditions: The effect of chromium

Cited by 42 publications

References 49 publications

Hot corrosion Type II of FeCr‐based model alloys for boiler and heat exchanger applications

Hot corrosion Type II of FeCr‐based model alloys for boiler and heat exchanger applications

A new solid‐state mode of hot corrosion at temperatures below 700°C

Corrosion protection in saline environment of a carbon steel coated (aluminum & three-layer painting system) by eats

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