THE INFLUENCE OF ADSORBED N IN THE INITIAL-STAGES OF OXIDATION OF IRON

The presence of a nitride layer on iron enhances the corrosion resista nce. Thus, it is of great importance to investigate the thermochemistr y of the Fe-N-O-H system. In this work, we report on the influence of adsorbed nitrogen in the surface region on the initial stages of room temperature oxidation of Fe(110). We combined ellipsometry and XPS wit h the high-energy ion beam technique elastic recoil detection (ERD). F rom the absolute coverages of N and O (and C and H) as determined with ERD and the results obtained with ellipsometry and AES, it appeared t hat adsorbed nitrogen (1.4 x 10(15) at cm(-2)) does not inluence the o xidation rate and the saturation oxide thickness. With XPS, also the c hemical state of the iron atoms in the oxide layer is found to be unaf fected, namely Fe2+ (corresponding to FeO). In addition, it followed t hat nitrogen remains under the oxide layer. This indicates that the ni trogen monolayer is an excellent marker for the study of mass transpor t across this interface. (C) 1998 Elsevier Science B.V. All rights res erved.