As a "green chemistry" tool, ultrasound irradiation of high intensity was successfully applied to formation of cerium/aluminum oxide anticorrosion protective layers on metal surfaces. The mechanism of metal surface modification in the presence of cerium(III) aqueous solution results from two components: activation of the metal surface by localized heating and activation of cerium ions which are diffused within liquid jets at high velocity to the metal surface. The ultrasonically increased reactivity of cerium and the developed surface of the metal stimulate formation of a novel type of cerium-enriched protective layer: cerium/aluminum oxide nanonetwork, where cerium oxide and aluminum oxide are interlaced in a mixed layer strongly connected to the metal surface. A combination of microscopic and spectroscopic methods was applied to study structure and morphology of the coatings as well as to optimize the ultrasound-assisted preparation method. The anticorrosion activity of the novel cerium/aluminum oxide system was demonstrated by using the scanning vibrating electrode technique.