A Surface‐Enhanced Raman Spectroscopy Study on Adsorption of Some Sulfur‐Containing Corrosion Inhibitors on Iron in Hydrochloric Acid Solutions

Abstract

The adsorption modes of some sulfur compounds, benzenethiol, phenylmethanethiol, and methyl phenyl sulfide on iron in 0.1M KC1 at pH 3.5 and 0.5M HC1 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 ~-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 0.5M HC1. In addition to the chemical adsorption b~ the formation of a a-bond, ~-electron interaction takes place between the surface and an aromatic ring of benzenethiol or methyl phenyl sulfide.Previous papers (1, 2) have dealt with surface-enhanced Raman scattering studies on the adsorption behavior of pyridine and N-ethyl-pyridinium bromide on iron in a 0.1M KC1 solution. Intense SERS signals of pyridine adsorbed on the iron surface have been detected using a SERSactive silver electrode completely covered with an iron layer of minimum thickness (5 monolayers, ca. 1.4 nm on the average). The adsorption and orientation modes of some nitrogen compounds at the iron surface in 0.5M HCI have also been determined by SERS spectroscopy (3, 4). Inhibition effects of these compounds on iron corrosion in the acid solution have been discussed.A number of organic sulfur compounds are known as effective corrosion inhibitors for various metals in acid solutions (5-7). Some of them react at the metal surface and their reaction products are adsorbed on the surface, resulting in inhibition of metallic corrosion (8-11). The SERS measurement of sulfur compounds seems appropriate for investigating the inhibition mechanism, including the adsorption of reaction products on the surface.In this study, the SERS spectra of benzenethio], phenylmethanethiol, and methyl phenyl sulfide adsorbed on iron in 0.1M KC1 at pH 3.5 and 0.5M HC1 were measured with a SERS-active silver electrode covered with deposited iron. Differences in the adsorption behavior and corrosion inhibition effectiveness of these compounds are discussed based on the SERS spectra and polarization curves. ExperimentalBenzenethiol (phenyl mercaptan) (~-SH, phenylmethanethiol (benzyl mercaptan) ~-CH2SH, and methyl phenyl sulfide ~-SCH~ were obtained as high-grade chemicals and purihed by distillation under a nitrogen atmosphere. Electrolyte solutions of 0.1M KC1 at pH 3.5 and 0.5M HC1 were prepared for the SERS and polarization measurements by diluting the respective analytical reagents with redistilled water and were deaerated by passing nitrogen gas through them.Electrodes of 9...

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Electrochemical and Theoretical Study of Pyrazole 4-(4,5-dihydro-1H-pyrazol-5-yl)-N,N-dimethylaniline (D) as a Corrosion Inhibitor for Mild Steel in 1 M HCl

“…In acidic solutions, the maximum inhibition efficiency was observed at an inhibitor concentration of 10 −3 M (97%). This result can be explained because organic inhibitors suppress the metal dissolution by forming a protective film adsorbed onto the metal surface, and preserve it from the corrosion medium [41].…”

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Tribulus terrestris Extracts: An Eco-Friendly Corrosion Inhibitor for Mild Steel in H2SO4 Medium

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