High chromium white cast irons are used in a number of applications in alumina refineries where wear
is a significant issue. However, recent case studies of failures of white irons in high temperature
digestion have suggested that significant corrosion of these materials is occurring and this may be
leading to accelerated wear rates. In this paper, the corrosion behavior of a series of high chromium
(Cr) white irons in concentrated caustic solutions is studied in the laboratory at temperatures from up to
280°C. The morphology of the oxide films is studied along with corrosion rates measured using weight
loss measurements, and this is correlated with compositional and microstructural variations in the white
irons. The failure mechanisms of these white irons involve preferential corrosion of the matrix,
particularly in circumstances where the matrix is pearlitic. Recommendations regarding the heat
treatment and compositions of white irons for use in high temperature digestion are made.
Key words: High Chromium Iron; Caustic corrosion; Alumina refining