Evaluation of vateria indicia leaves extract as a green source of potential corrosion inhibitor against mild steel corrosion in 1M HCl solution: electrochemical, and surface characterisation studies

The components of aqueous vateria indica leaves extract (VILE) were formulated as a green corrosion inhibitor for mild steel (MS) in 1 M HCl medium by weight change and electrochemical routes at 298 K. Nyquist plots indicated, as an increase the concentration of VILE, increases the resistance to charge transfer and lowers the value of electrical double layer capacitance. VILE affected both anodic and cathodic potentiodynamic curves decided that VILE components were mixed type. The addition of VILE concentration increases, progressively increasing the percentage inhibition efficiency and reaching a maximum of 93.22% at 150 ppm. The inhibition efficiency of the VILE was evaluated at elevated temperatures. Activation energy values were found to be higher in the presence of VILE compared to blank. The corrosion inhibition process was correlated through the Langmuir adsorption isotherm model using the Arrhenius equation. SEM and AFM images in the occurrence of VILE visualised that, MS surface was least affected compared to the corroded surface in the absence of an inhibitor. FT- IR spectral peaks suggested that the active groups present in the extract strongly interacted over the MS surface and formed a protective layer, this layer decreased the rate of corrosion to a greater extent.