Abstract
Surface‐enhanced Raman scattering (SERS) spectra of some nitrogen compounds adsorbed on iron in an acid solution were measured using an activated silver electrode covered with an appropriate amount of electrodeposited iron. Adsorption and orientation modes of the compounds, pyridine, aniline, N,N‐dimethylaniline, and N‐ethylpyridinium bromide, and their corrosion inhibition effects for iron in 
, were discussed on the basis of the SERS spectra and polarization curves. Pyridinium, anilinium, N,N‐dimethylanilinium, and N‐ethylpyridinium ions are adsorbed on the iron surface by electrostatic attraction between the cation and a negatively charged halide‐covered surface. The former two ions are mainly adsorbed in a perpendicular orientation, while the latter two are adsorbed in parallel with the surface under the influence of π‐electron interaction. An N,N‐dimethylaniline molecule is chemisorbed on the surface by formation of an iron‐nitrogen σ‐bond in addition to the electrostatic adsorption of its cation.