ABSTRACT
The high temperature oxidation of a series of nominally identical chromium samples has been examined, along with samples subjected to different hydrogen annealing treatments. The oxidation behaviour of the samples varied considerably, as did the effectiveness of hydrogen annealing. Some of the chromium samples were found to form flat adherent chromia scales, while the others formed convoluted non-adherent scales. When the samples which formed flat scales were contaminated with very low levels of sulphur or chloride salts the scale morphology changed and became convoluted and non-adherent. The microstructures of some of these scales have been examined using TEM techniques so that their microstructure and the effects of sulphur can be correlated.
