Thin films (about 10 nm) of Y2O3 have been deposited by a Langmuir-Blodgett processing technique onto a variety of substrates : type 304 stainless steel, low carbon steel, titanium, zirconium and silicon. The substrates were afterwards oxidized in air at 800, 1000(304 steer), 400 (low C steel), 500 (Ti), 450 (Zr) and 1000 (Si) degrees C. The effects of the film on the oxide scale thickness and the interaction between Y2O3 and the oxide of the substrate have been studied by ion backscattering. In stainless steel, the Y2O3 film reduces the oxidation rate by orders of magnitude and Y is distributed throughout the oxide scale (1-10 at.% level). In other substrates, the effect on oxidation rate was less pronounced, but changes in the visual appearance often took place. The Y2O3 incorporation varied for the different substrates, and Y2O3 remained as a surface film in the cases of Ti and Si. Such films exhibited good adherence and could not be removed by wiping. The potential use of metal oxide thin films for surface analysis standards and diffusion marker studies is discussed.