Paralinear Oxidation of Chromium in O2 + H2O Environment at 600–700 °C
Journal article, 2008

The oxidation of chromium in dry O2 and in O2 + 10%H2O at 600 and 700 °C is studied. Scale morphology is investigated by several methods, including scanning electron microscopy (SEM) of cross sections prepared by focussed ion beam milling (FIB). In O2 + H2O at 600 and 700 °C, chromium forms a duplex scale consisting of an inner barrier oxide and a discontinuous outer oxide made up of blade-shaped crystals. Thermogravimetric (TG) measurements show that water vapour influences chromium oxidation by causing vaporization of the protective oxide, resulting in paralinear oxidation kinetics. An extension of the original treatment by Tedmon is deduced, which allows for the determination of the evaporation rate constant k s and the parabolic oxidation rate constant k d from TG data acquired during short exposures. The results show that k d is the same in dry O2 and in O2 + 10%H2O. Equivalently, the transport properties of chromia are the same in the two environments. The equilibrium constant of CrO2(OH)2 formation from chromia is reported. The activation enthalpy of the vaporization reaction is determined.

Oxidation of chromium - Water vapour effect - Chromia vaporization - Paralinear oxidation

Author

Bagas Pujilaksono

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Torbjörn Jonsson

Chalmers, Applied Physics, Microscopy and Microanalysis

Mats Halvarsson

Chalmers, Applied Physics, Microscopy and Microanalysis

Itai Panas

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Jan-Erik Svensson

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Lars-Gunnar Johansson

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Oxidation of Metals

0030-770X (ISSN) 1573-4889 (eISSN)

Vol. 70 3-4 163-188

Subject Categories

Other Chemistry Topics

Other Materials Engineering

Environmental Sciences

Condensed Matter Physics

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Created

10/8/2017