Abstract: Oxide scale formation on a C-steel surface has been investigated using linear heating rates ranging from 0.1ºC/min to 10ºC/min at high temperatures. The studies on the oxide scale formation at high temperature (650ºC) at slower heating rate (0.1ºC/min) shows that the kinetic regime is linear. X-ray diffraction measurements revealed that the scale constituents are significantly influenced by the heating rate. The adherence of the scale was improved by using slower heating rate (0.1ºC/min-≤650ºC), while above such degree the scale was susceptible to cracking and flaking out of the alloy surface. In fact, the development of oxide growth stresses can cause considerable scale cracking. As well, variation of the crystallite sizes under the aforementioned conditions might affect the scale stacking to the alloy surface. The secondary electron detector images of the oxide scale shows that the scale was imperfectly smooth and there were a number of voids and defects in the scale skin, especially at fast heating rate. This observation could be attributed to defects of the as-received alloy. In general, slower heating rate reduced the defects of the scale and improved its adherence.

Key words: C-steel, Oxide scale, Heating rate, Weight gain, XRD