The Inhibitive Effect of Traces of SO<sub>2</sub>on the Oxidation of Iron

Järdnäs, Anders; Svensson, Jan‐Erik; Johansson, Lars‐Gunnar

doi:10.1023/a:1027382702616

Cited by 23 publications

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“…The inhibitive effect of SO 2 on oxidation was attributed to small amounts of sulphate found at the gas/oxide interface [2]. Compositional profiling of the scales showed that sulphur was also enriched at the scale/metal interfaces.…”

Section: Introductionmentioning

confidence: 98%

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The Effect of Traces of SO2 on Iron Oxidation: A Microstructural Study

et al. 2007

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Pure iron has been exposed to pure O 2 and O 2 with 100 ppm SO 2 at 525°C for 1 and 24 h. The samples were investigated by FIB, SEM, TEM, EDX and EBSD. The oxide scales formed on iron at 525°C in O 2 and in O 2 + 100 ppm SO 2 are dense and adherent and consist of three layers. The outermost layer consists of hematite. Beneath it there is a duplex-magnetite scale. The two magnetite layers are separated by a straight interface. It is concluded that the inner-magnetite layer grows inward while the outer magnetite layer grows outwards. In the presence of SO 2 the inner-magnetite layer is much thinner, iron sulphate forms at the oxide surface and discrete iron sulphide grains nucleate at the metal/oxide interface. The amount of sulphide at the metal/oxide interface increases with exposure time. The oxidation of iron in oxygen at 525°C is inhibited by 100 ppm SO 2 . The inhibitive effect of SO 2 is attributed to iron sulphate that blocks active sites on the hematite surface, slowing down the formation of oxygen ions. This explains the strong inhibition of the inward growth of magnetite by SO 2 . There is also a marked effect on the morphology of the outer oxide, producing hematite whisker growth and a less porous surface in the presence of SO 2 .

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Section: Introductionmentioning

confidence: 98%

“…It was recently shown that the oxidation rate of pure iron in O 2 is slowed down by traces of SO 2 (1-1000 ppm) in the temperature range 450-600°C [2]. The inhibitive effect of SO 2 on oxidation was attributed to small amounts of sulphate found at the gas/oxide interface [2].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Traces of SO2 on Iron Oxidation: A Microstructural Study

et al. 2007

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“…En otro estudio realizado sobre muestras de hierro altamente puro (99%) y empleando una mezcla de gases con HCl en 4 x 10 -4 % (4 ppm), agua 6.1% y nitrógeno (balance) a una temperatura de 400 °C, se obtuvo una cinética parabólica, en la cual la corrosión inicia rápido y se estabiliza con el tiempo, formando además capas de óxido muy compactas sobre la superficie [9]. El SO 2 por sí solo aumenta la pérdida de metal en ambientes a alta temperatura [10] y cuando se encuentra en presencia de HCl en dichos ambientes el efecto agresivo se incrementa aún más [5]. Bajo sucesivas exposiciones a estos ambientes, la herrumbre se vuelve más porosa, frágil y poco adherente, quedando expuesto el material metálico y continuando así su ataque [5].…”

Section: Análisis De Los Productos De Corrosión Encontradosunclassified

“…De otro lado, empleando el diagrama de estabilidad Fe-O-S para 500 °C [10] Finalmente el potencial de carburización del metal se puede calcular a partir de las presiones parciales del CO, CO 2 y O 2 y el diagrama de estabilidad Fe-C-O [13]. A partir de los datos de la tabla 2 para una temperatura de 500 °C, se encuentra que a esas condiciones el potencial de carburización es muy bajo y la fase más estable es el Fe 2 O 3 , en concordancia con los análisis FTIR y DRX.…”

Section: Análisis De Los Productos De Corrosión Encontradosunclassified

Análisis De Corrosión en Ductos De Conducción De Gases en Una Planta De Clinker

Carvajal

Echeverría

2009

Ingeniare. Rev. chil. ing.

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RESUMENEn este trabajo se presentan los resultados de un estudio detallado de las causas del deterioro observado en ductos metálicos de una planta productora de cemento. Para el análisis, se inició con una minuciosa inspección visual, tomando muestras de sustratos, productos de corrosión y gases de proceso. Al mismo tiempo se realizaron medidas de potencial de estructura, espesores de pared y temperaturas de superficies. Para la evaluación de la agresividad del ambiente se instalaron captadores de contaminantes (cloruros, sulfatos y óxidos de nitrógeno). Las muestras recolectadas se analizaron por medio de microscopia óptica y electrónica de barrido, espectroscopia EDS, difracción de rayos X, espectroscopia infrarroja y cromatografía iónica. Los gases se analizaron in situ siguiendo el procedimiento EPA-2. Los resultados para las superficies externas indican una atmósfera con agresividad C3 según la norma ISO 9223, observando influencia de la alta temperatura, largos periodos de humectación, material particulado y errores en la selección del sistema de protección. Las capas de productos al exterior son uniformes, compactas y son compuestas principalmente por hematita. Al interior de los ductos se presentan procesos de sulfurización y oxidación; el ataque por azufre es localizado y genera perforación de las paredes metálicas. Los productos encontrados son mayormente sulfatos de hierro y Fe 2 O 3 . Los procedimientos empleados y los resultados obtenidos son útiles para la toma de decisiones en mantenimiento y protección contra la corrosión de este tipo de instalaciones.Palabras clave: Oxidación, corrosión atmosférica, corrosión a alta temperatura, evaluación de corrosividad. ABSTRACT The results of a detailed study of the causes of deterioration, observed in metallic ducts in a cement

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“…Typically the presence of sulphur strongly increases the corrosion rate, but the influence of sulphur on corrosion can be complicated, as in the form of sulphur dioxide it can also slow down corrosion. The phenomenon is dependent on time, current environment, gas partial pressures and alloying elements [3][4][5][6][7][8]. It has been suggested that oxide scales developing in moist oxygen/carbon dioxide atmospheres are not well protective and internal carburisation may occur [5,9,10].…”

Section: Introductionmentioning

confidence: 99%

Performance of superheater materials in simulated oxyfuel combustion conditions

Tuurna

Pohjanne

Yli-Olli

2013

Materials & Corrosion

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Oxyfuel fired combustion has the potential to increase the fireside corrosion rates comparing to air firing combustion as a result of the increasing amounts of aggressive combustion products due to recycling of flue gas. The changes in the combustion gas chemistry will also affect the chemistry and formation of deposits, with potentially increasing corrosion and internal attack of the boiler components that are in contact with the combustion and flue gas environment. As the currently available information on the corrosion rates under oxyfuel conditions is still limited, and partially also contradicting, corrosion testing of existing boiler materials under high carbon dioxide combustion environments with the relevant oxygen, water vapour and impurity concentrations and deposits is very much needed. The work describes the laboratory testing of selected alloys (EN 1.4922, UNS S34710, UNS S31042, UNS S31035, A263 and A617) under simulated oxy-and air-firing combustion conditions with and without calcium carbonate-calcium sulphate deposit at 600 and 650 8C. The results showed that the corrosion resistance increased when the chromium content increased but without added impurities like sulphur and chlorides, the simulated oxyfuel conditions did not result in more severe corrosion than under air-fired environment. No carburisation of the metal substrate was observed after exposure to simulated oxyfuel gas atmospheres without deposit, although some carbon enrichment was detected near the oxide-metal interface. With extended exposure time, the oxide scale properties may change to enable metal carburisation. The exposure with deposit at 650 8C resulted in corrosion of all tested alloys and clear carburisation of steels EN 1.4922 and UNS S34710. Corrosion and microstructural changes, like carburisation, may reduce mechanical performance such as creep and/or fatigue strength and ductility, and thus the expected component life.

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The Inhibitive Effect of Traces of SO₂on the Oxidation of Iron

Cited by 23 publications

References 8 publications

The Effect of Traces of SO2 on Iron Oxidation: A Microstructural Study

The Effect of Traces of SO2 on Iron Oxidation: A Microstructural Study

Análisis De Corrosión en Ductos De Conducción De Gases en Una Planta De Clinker

Performance of superheater materials in simulated oxyfuel combustion conditions

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The Inhibitive Effect of Traces of SO2on the Oxidation of Iron

Cited by 23 publications

References 8 publications

The Effect of Traces of SO2 on Iron Oxidation: A Microstructural Study

The Effect of Traces of SO2 on Iron Oxidation: A Microstructural Study

Análisis De Corrosión en Ductos De Conducción De Gases en Una Planta De Clinker

Performance of superheater materials in simulated oxyfuel combustion conditions

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The Inhibitive Effect of Traces of SO₂on the Oxidation of Iron