The beneficial effect of yttrium addition on the oxidation behaviour of the 304 stainless steel, under isothermal conditions at 1000 degreesC in air, has been investigated. Two modes of introduction of the reactive element were studied, ion implantation and solgel coating. The thermogravimetric results show in both cases a significant reduction of the scale growth rate. In situ X-ray diffraction (XRD) technique reveals that this reduced oxidation rate is owing to the inhibition of the growth of iron-rich oxides. The present results support that yttrium promotes the intensive formation of the thin protective continuous chromia rich layer at the oxide-metal interface which acts as a diffusion barrier for iron. The study also underlines a cooling effect on the oxide scale composition. (C) 2002 Elsevier Science B.V. All rights reserved.