Protection contre la corrosion de l’acier A9 en milieu acide par des inhibiteurs verts

Abstract

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.