Inhibition of corrosion of mild steel pipeline carrying simulated oil well water by Allium sativum (garlic) extract

• S.C. Joycee^1,2, A.S. Raja², A.S. Amalraj³ and S. Rajendran¹

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

Abstract: The inhibiting effect of Allium sativum in controlling corrosion of mild steel in simulated oil well water (SOWW) in the absence and presence of Zn²⁺ has been investigated by different techniques like weight loss method, potentiodynamic polarization and electrochemical impedance spectroscopy for different concentrations of the plant extract. The formulation consisting of 10 mL of (10% aqueous extract) Allium sativum (garlic extract) and 50 ppm of Zn²⁺ provides 87% of inhibition efficiency. The results indicate that the corrosion inhibition efficiency increased on increasing plant extract concentration. The inhibitor system was found to be a cathodic inhibitor with the optimum inhibition concentration of 10 mL of Allium sativum and 50 ppm of Zn²⁺ in potentiodynamic polarization study. The corrosion potential is shifted from –777 mV vs. SCE to –880 mV vs. SCE. The linear polarization resistance (LPR) value increases from 482 Ohm·cm² to 1831 Ohm·cm². The corrosion current decreases from 1.034×10^–4 A/cm² to 0.1515×10^–4 A/cm². These factors confirm that the Allium sativum controls the corrosion of mild steel in SOWW. The AC impedance spectra confirm that the protective coating is very stable as revealed by the fact that in the presence of inhibitor on mild steel, the charge transfer resistance increases, impedance increases, whereas double layer capacitance decreases to a great extent. Surface analysis has been carried out to find out the surface morphology of the mild steel in the presence and absence of the inhibitor. The obtained results show that the Allium sativum extract acts as a good inhibitor for the corrosion of mild steel in SOWW.

Keywords: Allium sativum, corrosion inhibitor, simulated oil well water, polarisation study and AC impedance spectra, AFM

Int. J. Corros. Scale Inhib., 2021, 10, no. 3, 943-960
doi: 10.17675/2305-6894-2021-10-3-8

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