Rosemary extract as scale and eco-friendly corrosion inhibitor for carbon steel in HCl medium

• H.F. Emrayed¹, N.A. Mousa², H.M. Adress Hasan¹, K.A. Abdulghani¹, H.M. Moftah¹ and A.S. Fouda³

¹ Chemistry Department, Faculty of Science, Omar Al-Mukhtar University, Albyda, Libya
² Lybyan Academy for Postgraduate Studies, Tobruk, Libya
³ Chemistry Department, Faculty of Science, Mansoura University, Mansoura 35516, Egypt

Abstract: The inhibitory effect of the Rosemary extract on the corrosion of carbon steel alloys in 1 M hydrochloric acid was tested. Chemical method such as weight loss (WL) and electrochemical methods such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were used for research. The weight loss method revealed that at 100 ppm, the extract offers 89.2% inhibition efficiency (IE) to carbon steel (CS) immersed in a 1 M HCl solution. The polarization study revealed that a mixed type of inhibitor is present in the presence of an inhibitor system. The obtained results from EIS showed that the gradual increase in inhibitor concentration and time of immersion leads to a progressive increase in inhibition efficiency. The protective layer formed on the metal surface was confirmed by using EIS technique and this confirmed by the fact that there is an increase in the charge transfer resistance (R_ct) value and a decrease in the double layer capacitance (C_dl) value. The adsorption of the extract obeyed the Langmuir adsorption isotherm, and the adsorption behavior was analyzed, revealing a combination of physical and chemical interactions (a mixed type of adsorption) with Gibbs free energy calculations indicating favorable adsorption processes. Inhibition efficiency and activation factors were determined in the presence and absence of Rosemary extract. Hence, Rosemary extract has a good corrosive-inhibitive effect on carbon steel in hydrochloric acid solutions. The surface morphology of CS was tested using scanning electron microscopy (SEM) which indicates the shape of the surface and atomic force microscope (AFM) which investigates the roughness of the metal surface before and after the addition of the inhibitor. It turned out that all methods used were consistent with each other.

Keywords: carbon steel alloy, corrosion inhibition, hydrochloric acid, Langmuir isotherm, Rosemary extract

Int. J. Corros. Scale Inhib., 2025, 14, no. 4, 2133-2154
doi: 10.17675/2305-6894-2025-14-4-21

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