Corrosion inhibition effect of citrus sinensis essential oil extract on plain carbon steel in dilute acid media

Abstract

The inhibition performance of essential oil extracts of citrus sinensis (CS) on the corrosion of plain carbon steel (PCS) in 0.5 M H2SO4 and 0.5 M HCl solution was evaluated by weight loss measurement, potentiodynamic polarization technique, optical macroscopy and ATF-FTIR spectroscopy. CS more effectively inhibited PCS corrosion in HCl solution compared to H2SO4 with optimal inhibition result of 81.61% in HCl and 76.95% in H2SO4 from weight loss measurement. The corresponding values from potentiodynamic polarization are 94.90% in HCl and 76.93% in H2SO4 solutions respectively. Inhibition efficiency generally decreased with respect to exposure time, but increased with increase in inhibitor concentration in both acids. The inhibition performance of CS was observed to be mixed type inhibition effect in both acids with dominant cathodic inhibition reaction mechanism at 6%-10% CS concentration in HCl solution. CS influenced the anodic cathodic polarization plots in H2SO4 solution through surface coverage of the steel inhibiting the redox electrochemical process. In HCl significant influence of the anodic-cathodic polarization plots results in pseudo passivation behavior during potential scanning. Inhibition. FTIR spectra peaks showed aggregation of CS molecular functional groups with decreased transmittance over a wide spectrum in corroded H2SO4 solution compared to specific spectra peaks in HCl with decreased transmittance due to limited absorption of protonated CS molecules. Optical images of corroded and non-inhibited PCS specimen from both acids exhibited severe surface degradation with macro pits visible on the steel from H2SO4 solution. The inhibited steel from both acids displayed improved surface morphology due to surface protection effect of CS molecules.

Keywords

• Corrosion
• Adsorption
• Carbon steel
• Inhibitor