To enhance the inner surface of microchannel reactors, porous metal oxide coatings based on alumina, silica, and titanium oxide have been developed as support for catalytically active components. The oxides were made by the sol-gel process. Thin film coating was accomplished by dip coating using an Fe-based alloy as support. The influence of the sol composition, sol viscosity, and thermal treatment procedure on the surface enhancement factor and the porosity of the coating was investigated. The resulting surface enhancement factor reached 800 m(2)/m(2).