Electrochemical action of Citrus reticulata and Pelargonium oil concentrates on 1018 carbon steel corrosion in anionic solution

Corrosion inhibition of Pelargonium (Pe) and Citrus reticulata (Cr) oil concentrates and their admixture (PeCr) on 1018 carbon steel (18CS) was studied in 0.5M H2SO4 and HCl media with electrochemical polarization technique, potential-time evaluation (OCP), coupon computation, optical image assessment, ATF-FTIR spectroscopy and X-ray diffractometry. Polarization data showed Pe performed effectively only at the highest concentrations in H2SO4 (3% and 3.5%) with optimal inhibition performance of 91.56% while in HCl effective corrosion inhibition occurred at all concentrations considered with optimal value of 87.32% at 2.5% concentration. Cr concentrate performed adequately at all concentrations in H2SO4 and HCl solutions with utmost values of 78.12% and 91.87%. PeCr performed more efficiently at all concentrations in HCl with utmost value of 95.46%. PeCr utmost inhibition performance in H2SO4 was below 70%. Coupon measurement showed the concentrate performances in HCl are independent of time/concentration, and generally attained stability from 72 to 96 h of exposure. This contrast their performance in H2SO4 which is significantly dependent on time/concentration. OCP plots shows the presence of Pe in H2SO4 and HCl, Cr in H2SO4 and PeCr in H2SO4 heightens the thermodynamic tendency of 18CS to corrode in view of its optimal inhibition outputs compared to Cr and PeCr in HCl whose plots decreased the thermodynamic tendency. ATF-FTIR data depict significant decrease in transmittance of reactive groups for Cr in H2SO4 and HCl media at all wavenumbers due to adsorption. Transmittance of Pe and PeCr concentrates reactive groups increased after corrosion signifying the nature of their inhibition mechanism. Optical representations of protected and non-inhibited 10CS surfaces substantially differed from each other. X-ray diffractometry identified corrosive precipitates on the steel without concentrate addition. In the presence of the concentrates, in the presence of the concentrates the phases compounds identified on the inhibited steel were non-corrosive.