Surface treatment and corrosion protection of mild steel by the oily extracts of olive mill waste cake

The fight against the phenomenon of corrosion has become a necessity given the annual costs lost at the industrial level. The goal of this work is to measure the efficacy of two oil extracts from olive mill waste cake for mild steel in 1 M hydrochloric acid solution at inhibiting corrosion. It was determined by gravimetry, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and quantum chemical calculations by Monte Carlo simulation. Surface morphology was detected using scanning electron microscopy coupled to an EDX probe (SEM–EDX), and molecule adsorption was detected using UV–visible spectroscopy. Experimental results obtained by the gravimetric method showed that the methanol extract is more efficient than the hexane extract. These results are in agreement with potentiodynamic polarization and electrochemical impedance spectroscopy. They achieved 90% and 88% inhibition efficiency at 298 K for the methanol and hexane extract, respectively, which decreased with decreasing inhibitor concentrations. Potentiodynamic polarization studies evoked that the extracts are mixed-type inhibitors and impedance measurements showed that the double-layer capacitance (Cdl) increases with decreasing concentration of the inhibitors. Graphical abstract