Inhibition effects of orange peel extract on the corrosion of Q235 steel in CO 2 -saturated and CO 2 /H 2 S coexistent brine solutions

The inhibition effects of orange peel extract (OPE) on the Q235 carbon steel corrosion in CO2-saturated and CO2/H2S coexistent brine solutions were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analyses. The electrochemical measurements show that OPE can effectively retard the corrosion of Q235 steel induced by CO2 and CO2/H2S. OPE exhibited higher corrosion inhibition efficiency in CO2-saturated brine solutions than in CO2/H2S coexistent brine solutions. Inhibition efficiencies of 97.6 and 73.1% were achieved with 1000 mg L−1 OPE in CO2 and CO2/H2S brine solutions, respectively. The double-layer capacitance values of the working electrodes decreased remarkedly after OPE was added in the brine solutions and continued to decrease gradually with the increase of the dosage of OPE. OPE is rich in oxygen- and nitrogen-containing groups as revealed by Fourier transform infrared (FT-IR) analysis and functions via the adsorption of these groups on the steel surface according to the XPS analysis. The adsorption behavior of these OPE moieties follows the Langmuir adsorption isotherm.