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Studies on high temperature corrosion reactions involving metal oxides and sodium sulfate

Studies on high temperature corrosion reactions involving metal oxides and sodium sulfate Purpose – The purpose of this paper is to present the results of studies on the reaction of metal oxides such as Cr 2 O 3 and Al 2 O 3 with Na 2 SO 4 in flowing SO 2 (g) at 1,100 and 1,200 K. Design/methodology/approach – The oxides chosen for the studies were initial scaling products during the oxidation of industrial alloys and invariably are involved in hot‐corrosion reactions in the presence of molten salts. The thermo‐gravimetric studies for the system were carried out as a function of Na 2 SO 4 in the mixture. The different constituents in the reaction products were identified by XRD analysis and morphologies of the reaction products were discussed on the basis of optical metallography and scanning electron microscopic studies. The pH and conductivity of the aqueous solutions of reaction products were measured and an attempt made to functionalize these parameters with Na 2 SO 4 concentration in the mixture. Quantitative estimation of the soluble metal was carried out using an atomic absorption spectrophotometer. The formation of products was investigated by thermodynamic computation of free energies of the reactions and the study of relevant phase stability diagrams. Findings – Looking at the complex nature of the reactions, it is difficult to generalize the conductance studies, as many complex species are liable to hydrolyze in the aqueous solution. However, the break in few curves at certain mole fraction of Na 2 SO 4 indicates the presence of soluble complex species. Originality/value – The paper provides information regarding the reaction between a pertinent oxide and Na 2 SO 4 and proper identification of reaction products, useful for understanding the occurrence and importance of fluxing reactions and in the interpretation of hot corrosion mechanism and the development of new protective materials. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Anti-Corrosion Methods and Materials Emerald Publishing

Studies on high temperature corrosion reactions involving metal oxides and sodium sulfate

Anti-Corrosion Methods and Materials , Volume 55 (3): 7 – May 23, 2008

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Publisher
Emerald Publishing
Copyright
Copyright © 2008 Emerald Group Publishing Limited. All rights reserved.
ISSN
0003-5599
DOI
10.1108/00035590810870428
Publisher site
See Article on Publisher Site

Abstract

Purpose – The purpose of this paper is to present the results of studies on the reaction of metal oxides such as Cr 2 O 3 and Al 2 O 3 with Na 2 SO 4 in flowing SO 2 (g) at 1,100 and 1,200 K. Design/methodology/approach – The oxides chosen for the studies were initial scaling products during the oxidation of industrial alloys and invariably are involved in hot‐corrosion reactions in the presence of molten salts. The thermo‐gravimetric studies for the system were carried out as a function of Na 2 SO 4 in the mixture. The different constituents in the reaction products were identified by XRD analysis and morphologies of the reaction products were discussed on the basis of optical metallography and scanning electron microscopic studies. The pH and conductivity of the aqueous solutions of reaction products were measured and an attempt made to functionalize these parameters with Na 2 SO 4 concentration in the mixture. Quantitative estimation of the soluble metal was carried out using an atomic absorption spectrophotometer. The formation of products was investigated by thermodynamic computation of free energies of the reactions and the study of relevant phase stability diagrams. Findings – Looking at the complex nature of the reactions, it is difficult to generalize the conductance studies, as many complex species are liable to hydrolyze in the aqueous solution. However, the break in few curves at certain mole fraction of Na 2 SO 4 indicates the presence of soluble complex species. Originality/value – The paper provides information regarding the reaction between a pertinent oxide and Na 2 SO 4 and proper identification of reaction products, useful for understanding the occurrence and importance of fluxing reactions and in the interpretation of hot corrosion mechanism and the development of new protective materials.

Journal

Anti-Corrosion Methods and MaterialsEmerald Publishing

Published: May 23, 2008

Keywords: Corrosion; Chemical reactions; Corrosion inhibitors

References