ABSTRACT

Corrosion inhibition effect of an aqueous extract of oxalis acetulosa plant leaves on mild steel immersed in 1M hydrochloric acid. The corrosion inhibition efficiency and corrosion rates have been determined by weight loss method. The mechanistic aspects of corrosion inhibition have been studied by electrochemical studies such as potentiodynamic polarisation technique and electrochemical impedance spectroscopy (EIS). It is observed that as the concentration of the inhibitor increases the corrosion rate decreases and the inhibition efficiency increases. This is due to adsorption of the molecules of the active ingredients of the extract on the metal surface. A maximum inhibition efficiency of 89.60% is achieved by this inhibitor system. Potentiodynamic polarisation technique reveals that the inhibitor system functions as an anodic type of inhibitor, controlling anodic reaction preferably. It is observed that, in presence of inhibitor, linear polarization resistance (LPR) value increases from 405 ohm.cm2 to 1889.5 ohm.cm2 . Corrosion current (Icorr) decreases from 1.022 × 10-4 A/cm2 to 2.370 x 10-5 A/cm2 . Charge transfer resistance (Rt) value increases from 98.75 ohm.cm2 to 432.2 ohm.cm2 . Double layer capacitance (Cdl) value decreases from 1.6607 × 10-8 F cm-2 to 3.7945 × 10-9 F cm-2. The impedance value [log (z/ohm)] increases from 0.350 to 0.510. The phase angle value increases from 12.5 to 28.0o . Electrochemical studies reveal that a protective film is formed on the metal surface. The surface morphology of the protective film has been studied by SEM and AFM. The outcome of the study can be used in pickling industry, wherein, hydrochloric acid is used to remove the rust on the mild steel surface. Keywords: Acidic solutions, AFM, Mild steel corrosion, oxalis acetulosa plant leaves, Scanning Electron Microscopy and Weight loss method
Publication date: 01/11/2021

https://ijbpas.com/pdf/2021/November/MS_IJBPAS_2021_NOV_SPCL1128.pdf

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https://doi.org/10.31032/IJBPAS/2021/10.11.1128