Plant Doum (Hyphaenethebaica L.) as a safe corrosion inhibitor for carbon steel in a solution of HCl

• A.S. Fouda¹, A.Y. El-Etre² and M. Mahmoud²

¹ Chemistry Department, Faculty of Science, El-Mansoura University, Mansoura, Egypt
² Chemistry Department, Faculty of Science, Benha University, Egypt

Abstract: Plant Doum (Hyphaenethebaica L.) extract was studied as a corrosion inhibitor for carbon steel (CS) dipped in 1 M hydrochloric acid using chemical and electrochemical tests. From chemical tests based on mass loss (ML), the inhibition efficiency increased with increasing the concentration of Doum (Hyphaenethebaica L.) extract (up to 150 ppm). The adsorption isotherm of Doum (Hyphaenethebaica L.) extract on CS surface obeys the Langmuir adsorption isotherm. The inhibition efficiency improves on raising the concentration of the Doum (Hyphaenethebaica L.) extract and decreases with an increase in the temperature of the medium. This extract may form a film which acts as a barrier decreasing the contact area between the CS surface and the HCl solution. Doum (Hyphaenethebaica L.) extract acts as mixed inhibitor in HCl solution without modifying the mechanism of hydrogen evolution. From the EIS examination, we notice that with an increase in the concentration of Doum (Hyphaenethebaica L.) extract, the double layer capacitance decreased, but the charge transfer resistance increased. Thermodynamic parameters of activation and adsorption were calculated and explained. The sign of the free energy of adsorption implies that the adsorption process is spontaneous. The surface morphology of CS was examined by employing the SEM technique. The results obtained by all the methods are in good harmony.

Keywords: corrosion inhibition, carbon steel, Doum (Hyphaenethebaica L.), Langmuir isotherm, EIS, EFM

Int. J. Corros. Scale Inhib., 2021, 10, no. 4, 1547-1565
doi: 10.17675/2305-6894-2021-10-4-11

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