Olive leaf extract as natural corrosion inhibitor for pure copper in 0.5 M NaCl solution: A study by voltammetry around OCP

• Voltammetry around OCP is applied to the study of a corrosion inhibitor.
• Voltammetry around OCP is a useful complementary method to EIS.
• The olive leaf extract acts as a cathodic-type corrosion inhibitor.
• The inhibition efficiency increases with time during the 24 h experiments.
• The major phenolic compound of the olive leaf extract is oleuropein.

The inhibiting action of olive leaf extract on corrosion of copper in 0.5 M NaCl solution was investigated via potentiodynamic polarization and electrochemical impedance spectroscopy. For the highest inhibitor concentration considered here the inhibition efficiency reached 90% after 24 h of immersion. Polarization curves recorded around OCP were computer fitted with various kinetic laws to obtain detailed information on the inhibition process. This innovative procedure led to results consistent with those deduced from electrochemical impedance spectroscopy and confirmed that the olive leaf extract act as a cathodic-type corrosion inhibitor mainly hindering the transport and thus the reduction of dissolved O2. High performance liquid chromatography showed that oleuropein was the major compound of the leaf extract and thus more likely the main inhibiting species.