Résumé:
This work is dedicated to the study of the effect of olive leaf extract (OL), marjoram oregano
(MO), and their mixture (OL, MO) as green inhibitors on the corrosion of A9 steel in an acidic
medium (1M HCl), using electrochemical impedance spectroscopy (EIS), potentiodynamic
polarization, and gravimetric measurements. To better understand how the inhibitor acts
against corrosion, a thermodynamic study was conducted, along with the analysis of
different adsorption isotherms.
The results from the weight loss method and electrochemical techniques show that both
extracts effectively inhibit steel corrosion, especially their mixture, which can reach up to
90% efficiency at a concentration of 50 ppm. This inhibitor behaves as an anodic inhibitor.
The inhibitor molecules adhere to the steel surface according to the Langmuir isotherm,
indicating the formation of a monolayer. Moreover, the activation energy values suggest
that the adsorption is of the physisorption type. FTIR and UV-Vis spectra confirm the
simultaneous presence of functional groups such as O-H, C-O, and C=O.
The steel surface morphology was examined using optical microscopy. The findings show
that olive leaf extract, marjoram oregano extract, and their mixture effectively inhibit the
corrosion of A9 steel, form a protective film, and thus act as a good barrier against the
penetration of the corrosive medium to the metallic surface.
