Olive leaf extract as a green carbon steel corrosion inhibitor in brine solution saturated with CO2

Carbon steels are widely used in the process of oil production and therefore exposed to the constant action of the electrolytes, rich in dissolved gases, salts and organic acids. This results in significant corrosion failure, high costs and a negative environmental impact. The most common method of corrosion protection is the use of corrosion inhibitors, which is limited by economic and environmental requirements. The aim of this work was to investigate the effect of olive leaf extract as non-toxic, cost-effective corrosion inhibitor and the possibility of its application in the protection of J55 carbon steel used in tubing manufacturing in the oil industry. Electrochemical tests were performed after the steel was exposed to simulated realistic conditions. These conditions were as follows: chloride-carbonate solution saturated with CO2, stirred using a magnetic stirrer at 300 r min-1 speed at 35 °C temperature. The concentrations of 50 to 300 mg L-1 extract were added. Linear polarization in Eoc ± 250 mV potential field and the Tafel extrapolation method in the presence of the extract determined that the extract acts as a mixed type corrosion inhibitor with the predominant influence on the anodic process. Linear polarization resistance monitoring over a period of 24 hours has proven that the extract provides high protection from corrosion. Recorded electrochemical impedance spectra in the presence of the extract show the existence of the second time constant in the field of high frequency, indicating the presence of the inhibitor film on the surface of tested steels. This is further confirmed by the recording in FTIR spectra. All testing methods prove the extract’s high inhibitor efficiency against corrosion of J55 carbon steel in tested conditions.