The need for a more efficient coal power plant generation (e.g. oxyfuel technology) results in modified process parameters and enhanced corrosion. To reach the necessary service life of high temperature parts protective coatings may be a sufficient technical solution. A modified Yoldas sol (Al2O3 based) was used to coat X20CrMoV12-1 by spin coating. After appropriate heat treatments transition alumina coatings being about 400 nm thick were obtained. Oxidation studies were carried out in laboratory air at temperatures up to 650 degrees C for up to 500 h exposure time. In case of the uncoated sample a rough oxide layer formed on the surface and a remarkable weight gain (2.62 mg/cm(2)) were detected. The sol-gel alumina layer (mainly delta-Al2O3) demonstrated a high protection, i.e. a very low weight gain (0.05 mg/cm(2)). Diffusion of alloying elements into the coating was observed. No indication of spallation of the coating occurred. Local defects (2 mu m-30 mu m) in the coating led to the formation of iron-oxide islands. (C) 2013 Elsevier B.V. All rights reserved.