Corrosion mitigation by an eco-friendly inhibitor: Beta vulgaris (beetroot) extract on mild steel in simulated oil well water medium

• S.C. Joycee¹, A.S. Raja², A.S. Amalraj³ and S. Rajendran^1,4

¹ Department of Chemistry, Corrosion Research Centre, St. Antony’s College of Arts and Sciences for Women, Dindigul-624 005, India
² Department of Chemistry, G.T.N Arts College (Autonomous), Dindigul-624 005, India
³ Department of Physics, Sree Sevugan Annamalai College, Devakottai-630 303, India
⁴ Adjunct Professor, Pondicherry University, Puducherry, India

Abstract: The inhibition efficiency (IE) of an aqueous extract of Beta vulgaris (beetroot) in controlling corrosion of mild steel in simulated oil well water (SOWW) in the presence and absence of Zn²⁺ has been evaluated by weight loss method. The formulation consisting of 10% aqueous extract of Beta vulgaris extract and 50 ppm Zn²⁺ offers 94% inhibition efficiency to mild steel immersed in simulated oil well water. A synergistic effect exists between Beta vulgaris extract and 50 ppm Zn²⁺.The polarization study reveals that this formulation acts as a barrier film controlling the cathodic reaction predominantly. The corrosion potential is shifted from –777 mV SCE to –789 mV SCE. The inhibitor system functions as mixed type of inhibitor because the shift in corrosion potential is within 50 mV. The linear polarization value increases from 482 Ohm∙cm² to 1838 Ohm∙cm². The corrosion current decreases from 1.034∙10^–4 A/cm² to 1.887∙10^–5 A/cm². These factors confirm that the Beta vulgaris extract controls the corrosion of mild steels in SOWW. The AC impedance spectra confirm that the protective coating is very stable as revealed by the fact that in the presence of Beta vulgaris on mild steel, its charge transfer resistance increases, impedance increases, whereas double layer capacitance decreases. The surface morphology has been analyzed by SEM. FTIR spectra study leads to the conclusion that the Fe²⁺–betanin complex formed on the anodic sites of the metal surface controlled the anodic reaction, and Zn(OH)2 formed on the cathodic sites of the metal surface controlled the cathodic reaction. Synergism parameters are found to be greater than 1 indicating that a synergistic effect exists between Beta vulgaris and Zn²⁺. SEM study reveals that in presence of inhibitor system the surface of the metal becomes very smooth. The outcome of the study may be used in petroleum industry. The inhibitor formulation may be added along with mild steel pipelines carrying oil well water.

Keywords: Beta vulgaris, corrosion inhibitor, simulated oil well water, polarisation study, petroleum technology, FTIR, AC impedance spectra and SEM, synergism parameter

Int. J. Corros. Scale Inhib., 2022, 11, no. 1, 82-101
doi: 10.17675/2305-6894-2022-11-1-4

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