In order to ensure a good resistance to high temperature oxidation, the oxide scales formed on stainless steels should remain thin, rich in Cr with good adhesion properties to the metallic substrate. However, the formation of the protective Cr-rich oxide scale induces a decrease of the Cr concentration in the bulk zone underneath the oxide scale. The balance between Cr consumption in the oxide scale and Cr diffusion from the bulk is a key parameter for the steel durability: below a critical level, Cr depletion leads to a loss of the scale protectiveness, and nucleation and fast growth of non-protective Fe-rich oxide nodules happens.
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