Adsorption modes of dibenzyl disulfide, sulfide, and sulfoxide on bare and iron‐coated silver in 0.5 M HCl were studied by surface‐enhanced Raman scattering (SERS) spectroscopy. SERS spectra of these compounds were measured using a SERS‐active silver electrode uncovered or covered with an electrodeposited iron layer. SERS spectra of dibenzyl disulfide showed cleavage of a S‐S bond and adsorption of phenylmethanethiolate ion on the silver and iron‐deposited silver surface. Dibenzyl sulfide, which was chemisorbed on the metal surface by the formation of a coordinate bond, was not an effective inhibitor for iron corrosion in the acid solution. SERS spectra of dibenzyl sulfoxide on the metal surfaces in 0.5 M HCl exhibited cleavage of a S‐O bond to form dibenzyl sulfide through cathodic reduction and strong chemisorption of the sulfide thus formed on the surfaces, resulting in a high inhibition efficiency for iron corrosion. X‐ray photoelectron spectra for the iron surface inhibited with the sulfoxide suggested the formation of a multimolecular layer of the sulfide‐containing ferrous oxide and chloride on the surface.
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Ohno et al. (1993) studied this question.