Aqueous extract of Cassia fistula flower as green corrosion inhibitor for mild steel in simulated oil well water medium

• K. Kavitha^1,2, H. Benita Sherine¹ and S. Rajendran^3,4

¹ PG and Research Department of Chemistry, ThanthaiPeriyar Government Arts and Science College (Autonomous), Tiruchirappalli-620023, Affiliated to Bharathidasan University, Tiruchirappalli-620024, Tamilnadu, India
² PG and Research Department of Chemistry, National college (Autonomous), Tiruchirappalli-620001, Affiliated to Bharathidasan University, Tiruchirappalli-620024, Tamil Nadu, India
³ PG Department of Chemistry, Corrosion Research centre, St. Antony’s College of Arts and Sciences for Women, Dindigul-624005, Affiliated to Mother Teresa Women’s University, Kodaikanal, Tamil Nadu, India
⁴ Adjunct Professor, Centre for Nanoscience and Technology, Pondicherry University, Puducherry, India

Abstract: The inhibition efficiency of aqueous extract of Cassia fistula flower (CFF) in controlling corrosion of mild steel in simulated oil well water (SOWW) medium has been evaluated by weight loss method and electrochemical measurement (potentiodynamic polarization study). The extract has been characterized by Fourier Transform Infrared Spectroscopy (FTIR). The active ingredients present in the CFF have been identified by Gas Chromatography Mass Spectroscopy (GCMS). A maximum inhibition efficiency of 95% has been obtained at 10% of CFF extract. The polarization study reveals that this formulation acts as a barrier film controlling the cathodic reaction predominantly. The corrosion potential is shifted from –831 to –875 mV vs. SCE. The inhibitor system functions as mixed type of inhibitor because the shift in corrosion potential is less than 85 mV. The linear polarization resistance value increases from 501 Ohm·cm² to 1335 Ohm·cm². The corrosion current decreases from 7.688·10–5 A/cm2 to 2.593·10–5 A/cm². These factors confirm that the Cassia fistula flower extract controls the corrosion of mild steel in SOWW. The surface morphology has been examined with the help of scanning electron microscopy (SEM) and atomic force microscopy (AFM). It is observed that in presence of inhibitor the surface of the corroded metal becomes smoother. The findings have potential application in petroleum industry. The inhibitor extract can be added along with the simulated oil well water in pipeline made of mild steel.

Keywords: Cassia fistula flower, corrosion inhibitor, mild steel, simulated oil well water, electrochemical studies

Int. J. Corros. Scale Inhib., 2022, 11, no. 3, 1131-1146
doi: 10.17675/2305-6894-2022-11-3-14

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