Long term high temperature oxidation resistance of a nanoceria coated 316 SS under dry air conditions

In this work, nanoceria dip coated and uncoated 316 stainless steels were exposed to dry air at 1073-1273 K for times of up to 250 h. From this work, measured activation energies, Q = 256 kJ mol−1 and Q = 240 kJ mol−1 were found for coated and uncoated 316 SS, respectively. In the coated steel, the activation energy for oxidation cannot be attributed to a single mass transport mechanism. In addition, the scale morphologies, as well as the dominant oxide phases were determined by X-ray diffraction means. It was found that in the nanoceria dip coated steels, the scale was fine grained and highly adherent. Oxidation at increasing temperatures in the coated steels favored the development of the spinel ((Mn, Cr)3O4 structure and at 1273 K with the presence of Fe2O3 was severely hindered. In contrast, in the uncoated steel, a relatively thick scale, predominantly Fe2O3 developed and it exhibited severe damage through spallation and detachment from the steel substrate. Also, the resultant grain structure was rather coarse and it consisted of faceted grains with continuous nucleation/growth at grain ledges.