Effect of spinel and perovskite coatings on the long term oxidation of a ferritic stainless steel in H2/H2O atmosphere

In order to improve the oxidation behaviour of AISI441 ferritic stainless steel in H-2/H2O atmosphere at 800 degrees C, four oxide coatings were tested: two perovskites (La0.8Sr0.2MnO3 and LaNi0.6Fe0.4O3) deposited by screen printing and two spinels (MnCo2O4 and Co3O4) obtained by PVD technique. Isothermal oxidation tests performed up to 3000 h showed that the coating presence avoided Fe oxides growth, which occurs for the raw alloy in the same conditions. Moreover, a protective (Cr,Mn)(3)O-4/Cr2O3 layer formed between the substrate and the coating. Any presence of Cr was not detected within the coatings, indicating that all compositions were efficient in preventing Cr evaporation.