Effect of exposure time on the morphology of corrosion on high chromium white cast iron in high temperature caustic solutions

Authors

  • A. J. McLeod,

    1. CAST Cooperative Research Centre, Process Engineering and Light Metals Centre, Central Queensland University, P.O.Box 1319, Gladstone QLD 4680, (Australia)
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  • R. E. Clegg

    Corresponding author
    1. CAST Cooperative Research Centre, Process Engineering and Light Metals Centre, Central Queensland University, P.O.Box 1319, Gladstone QLD 4680, (Australia)
    • CAST Cooperative Research Centre, Process Engineering and Light Metals Centre, Central Queensland University, P.O.Box 1319, Gladstone QLD 4680, (Australia).
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Abstract

High chromium white irons are important candidate materials for use in alumina refineries to combat wear and corrosion. The effect of exposure time on the formation of oxide films was studied in a 23% Cr white cast iron exposed at 260 °C in 110 g/l caustic soda solutions. It was found that whilst well-formed octahedral M(II)O.M(III)2O3 spinel type oxides initially formed and spread across the surface of the material, these were gradually replaced by a background oxide with a higher Cr/Fe ratio and the morphology of the octahedral crystals became less well formed. Also, the oxidation was found to be predominantly in the matrix material, leaving carbide particles unsupported on the surface and in the later stages, significant corrosion was found along the carbide/matrix phase boundary.

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