Synergistic Effect between Fragaria ananassa and Cucurbita pepo L Leaf Extracts on Mild Steel Corrosion in Hydrochloric
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HYSICOCHEMICAL PROBLEMS OF MATERIALS PROTECTION
Synergistic Effect between Fragaria ananassa and Cucurbita pepo L Leaf Extracts on Mild Steel Corrosion in Hydrochloric Acid Solutions L. W. El Khatiba, H. T. Rahala, *, and A. M. Abdel-Gaberb aDepartment
of Chemistry, Faculty of Science, Beirut Arab University, Beirut Lebanon Department of Chemistry, Faculty of Science, Alexandria University, Ibrahimia, P.O. Box 426, Alexandria, 21321 Egypt *e-mail: [email protected]
b
Received March 27, 2020; revised April 15, 2020; accepted April 22, 2020
Abstract—The thermodynamic, inhibitive and synergistic properties of Fragaria ananassa (strawberry) and Cucurbita pepo L (zucchini) leaf extracts on the corrosion of mild steel in Hydrochloric acid solutions were examined by potentiodynamic polarization curves measurements and electrochemical impedance spectroscopy (EIS) technique as well as optical photographic study. Fourier transform infrared spectroscopy (FTIR) and UV-Spectroscopy were applied to predict the possible functional groups and constituents of both leaf extracts. Potentiodynamic polarization curves proved that Fragaria ananassa and Cucurbita pepo L leaf extracts act as mixed type inhibitors for mild steel in 0.5 M HCl solutions. Impedance plots indicated that the corrosion process occurred under activation control. Thermodynamic parameters proved that the formation of the activated complex is an endothermic association instead of a dissociation step. The inhibitive efficiency of these leaf extracts relies on their physical adsorption on the metal surface rather than the complexation with Fe2+ ions. Cucurbita pepo L leaf extract is more efficient than Fragaria ananassa as a corrosion inhibitor for mild steel in 0.5 M HCl. The synergistic effect between both extracts may be due to co-adsorption between their molecules, which could be either competitive or co-operative adsorptions. The synergistic parameter value S was higher than unity indicating a cooperative synergistic effect. Keywords: mild steel, strawberry, zucchini, HCl, thermodynamic, mechanism, synergistic effect DOI: 10.1134/S2070205120050111
1. INTRODUCTION Despite of the great challenge from advanced alloys, mild steel still a widespread metal applied in petrochemical, oil and nuclear industries for the manufacture of reaction vessels, storage tanks and pipelines [1, 2]. The acid pickling or cleaning of mild steel surface is a commonly indispensable process to get rid of oxides and rust accumulated on the surface during annealing. Sulfuric, Phosphoric, hydrochloric and nitric acids are the most used in such pickling processes [3–7]. However, they are quite corrosive to metals. In fact, the employment of corrosion inhibitors to control such metallic corrosion had been accounted to be a practical method [8–14]. Though, lately researchers have paid attention to low cost ecofriendly inhibitors and drawn their efforts towards natural products and plant extracts [4, 15–30]. These herbal extracts are rich in naturally synthesized chemical compounds [31].
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