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.