In Situ Raman Spectra of Pyridine and Pyridinium Chloride Adsorbed on Iron in K 2 SO 4 and H 2 SO 4 Solutions

A study on adsorption behavior of organic compounds on iron in a sulfate solution is of importance to an investigation of their inhibition mechanism for iron corrosion in the solution. Surface‐enhanced Raman scattering (SERS) spectra of pyridine and pyridinium chloride adsorbed on iron in 0.1 M K 2 SO 4 at pH 3.5 and 0.25 M H 2 SO 4 were measured using a SERS‐active silver electrode covered with an iron layer of minimum thickness. It was concluded from the spectra that a pyridine molecule is chemisorbed on the iron surface in 0.1 M K 2 SO 4 . A weak SERS spectrum of pyridinium ion adsorbed on iron was observed in 0.25 M H 2 SO 4 because of a low adsorbability of the ion on the iron surface in the solution.