The effect of exposure of Inconel alloy X-750 to air at 1150°C on creep at 700°C and 400 MPa has been investigated. Contrary to the findings for exposure at 1050°C, exposure to air at 1150°C does not impair creep ductility. This is attributable to oxygen diffusion into the alloy at 1150°C being impeded. Evidence is given here to show that during exposure to air at 1150°C diffusion of chromium is fast enough to reach the surface and form a chromium oxide scale, which acts as a barrier to further oxygen diffusion.