Synergistic inhibition between 1-octadecanethiol and iodide ions on X60 pipeline steel for corrosion protection

Abstract

The corrosion protection of carbon steel in 1 M HCl by 1-octadecanethiol (ODT) alone and in combination with iodide ions was investigated at ambient temperature using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. Results obtained showed that ODT alone offered low corrosion protection ability at very low concentrations. However, on addition of iodide ions, the corrosion protection potential was enhanced due to synergistic effect. Potentiodynamic polarization data revealed that ODT acts as mixed-type inhibitor influencing both the cathodic hydrogen evolution and anodic metal dissolution reactions. Adsorption of ODT onto the carbon steel surface followed Langmuir adsorption isotherm model. The existence of synergism phenomenon between ODT and iodide ions was confirmed from synergism parameter, which was found to be greater than unity. Quantum chemical calculations provide greater insight into the mechanism of electron transfer and mechanistic aspects of ODT on steel surface.