Fullerenes were deposited on iron substrates via thermal evaporation under high vacuum conditions at room temperature. After deposition the samples were subjected to ion irradiation from a radiofrequency plasma with the samples held at room temperature. The gases used for irradiation were argon and nitrogen, respectively. The process leads to an opening of the fullerene cage structure and forms an extended network of amorphous carbon in the upper region of the fullerene layer. Changes in the structure of the films due to the treatment were analyzed by Raman spectroscopy. In order to determine the porosity of as-deposited and post-deposition treated fullerene films, electrochemical polarization measurements were carried out in aqueous corrosive environment. Thus the dissolution current of the iron substrate through the films was measured. The results show that plasma treatment leads to formation of amorphous carbon with a considerably lower porosity than the fullerene film. Hence, ion irradiation improves the coverage of the film and its corrosion protection ability. (C) 2003 Elsevier B.V. All rights reserved.