Eco-friendly corrosion inhibitor for mild steel in acidic media

• S. El-Housseiny^1,2, A.M. Abdel-Gaber³, H.T. Rahal⁴ and F.T. Beqai⁵

¹ Chemistry Department, Faculty of Sciences and Arts, Jouf University, Jouf, Saudi Arabia
² Faculty of Science, Chemistry Department, Kuwait University, Kuwait
³ Department of Chemistry, Faculty of Science Alexandria University, Ibrahimia, P.O. Box 426, Alexandria, 21321, Egypt
⁴ Department of Chemistry, Faculty of Science, Lebanese International University, Lebanon
⁵ Department of Chemistry, Faculty of Science, Beirut Arab University, Lebanon

Abstract: In recent decades, green chemistry has become a tool for sustainable growth in a variety of sectors, and the reorientation of the use of environmentally friendly alternatives is gaining attention in the field of corrosion protection. In this context, Prunus Dulcis (PD) leaf (Almond) extract, has been assessed as a potential green inhibitor for mild steel corrosion in 0.5 M H₃PO₄ and 0.5 M H₂SO₄ solutions at 30°C by electrochemical impedance spectroscopy (EIS) technique and potentiodynamic polarization curves measurements. Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectroscopy (GC-MS) results revealed that PD leaf extract contains carbonyl groups, aromatic rings, and double bonds as well as nitrogen containing compounds that make it a prospective corrosion inhibitor for mild steel. Polarization curves measurements indicated that PD is classified as a mixed type inhibitor in 0.5 M H₃PO₄ solutions while a cathodic type inhibitor in 0.5 M H₂SO₄ solutions. Nyquist plots revealed that the dissolution process occurs under activation control. The impedance responses indicated that the corrosion process occurs under activation control. To determine the mechanism of inhibition of PD leaf extract, different adsorption isotherms including Langmuir, Kinetic-thermodynamic, Flory-Huggins, and Temkin model were studied. The formation of the activated complex is an endothermic association rather than a dissociation process, according to thermodynamic characteristics. Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) proved that the inhibitive performance of PD leaf extract could be ascribed to the physical adsorption of the extract active ingredients forming a protective barrier on mild steel surface. PD leaf extract is more effective as a corrosion inhibitor for mild steel in 0.5 M H₃PO₄ than in 0.5 M H₂SO₄ solutions. In brief, our results show that PDF leaf extract is a new, ecologically safe, and effective corrosion inhibitor for the protection of mild steel in acidic media.

Keywords: corrosion, inhibitors, acid media, EIS, EDS, SEM

Int. J. Corros. Scale Inhib., 2022, 11, no. 4, 1516-1538
doi: 10.17675/2305-6894-2022-11-4-6

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