The adsorption modes of some sulfur compounds, benzenethiol, phenylmethanethiol, and methyl phenyl sulfide on iron in at pH 3.5 and were investigated by surface‐enhanced Raman scattering (SERS) spectroscopy. Spectra of these compounds adsorbed on iron were measured using a silver electrode completely covered with an electrodeposited iron layer. The SERS spectra of benzenethiol and phenylmethanethiol did not show S‒H bonds for the species adsorbed on the iron surface in the solutions. It is concluded that all the compounds are chemisorbed on the iron surface in both solutions, and that thiolate ions of the former two inhibitors are adsorbed by the formation of stronger σ‐bonds between sulfur and iron atoms, resulting in higher inhibition efficiencies for these compounds than for methyl phenyl sulfide. No electrostatic adsorption of the sulfonium cation occurs on the iron surface in . In addition to the chemical adsorption by the formation of a σ‐bond, π‐electron interaction takes place between the surface and an aromatic ring of benzenethiol or methyl phenyl sulfide.