Evaluation of Tamarix Aphylla extract as an eco-friendly corrosion inhibitor for carbon steel in saline medium

Abstract

The concentration effect of Tamarix Aphylla (TA) extract was investigated as a green corrosion inhibitor for carbon steel (E24) in saline solution. The extract was obtained by the maceration method using ethanol solution. Subsequently, the composition of the TA extract was characterized through a combination of phytochemical analysis, Fourier Transform Infrared Spectrometer (FTIR), and High-Performance Liquid Chromatography (HPLC). The TA extract was found to be rich in polyphenols (582.5 mg GAE per g of dry weight), with vanillic and para-coumaric acids as the primary polyphenolic compounds. Additionally, the extract demonstrated strong antioxidant activity, with an IC₅₀ value of 5.33 mg mL⁻¹. These results suggest that TA could be an effective corrosion inhibitor. For this reason, it was tested as an eco-friendly corrosion inhibitor for E24. Corrosion inhibition performance was assessed using several electrochemical techniques: open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (Tafel) measurements to determine the optimal inhibitor concentration for minimising the corrosion rate of steel. The morphology of the steel surface was analyzed using scanning electron microscopy (SEM). The results indicated that the TA extract, at an optimal concentration of 50 ppm, provides excellent corrosion protection in saline solution (∼98% inhibition according to Tafel and ∼80% according to EIS). TA acted as an anodic inhibitor. In this study, the extract effectively formed a protective film on the steel surface, enhancing its resistance to corrosion. At higher concentrations, the protective efficiency decreased, likely due to heterogeneous film formation, as shown by SEM-EDX analyses. TA adsorption followed the Langmuir isotherm. Thermodynamic and electrochemical data suggest mainly physisorption. The corrosion inhibition mechanism was shown to be strongly dependent on the extract concentration, and a comprehensive explanation is provided below, suggesting a potential for practical application in corrosion prevention.