Selective Oxidation of Chromium by O2 Impurities in CO2 During Initial Stages of Oxidation.

This study shows that the corrosion behaviour of 12 wt% Cr steel in CO ₂ at 550 °C is determined in the first stage of oxidation by reaction with O ₂ impurities. Depending on the amount of theses impurities and the thermal ramp rate, selective oxidation of chromium could lead to the formation of a protective chromium-rich oxide. An oxidation model describing qualitatively the nature of the oxide layer formed in the initial period of oxidation is presented. From these observations, surface engineering processes for protecting 9–12 wt% chromium steels from fast corrosion rate have emerged. [ABSTRACT FROM AUTHOR]