Electrochemical and Morphological investigations of Elettaria cardamomum pod extract as a green corrosion inhibitor for Mild steel corrosion in 1 N HCl

Abstract

The corrosion inhibition performance of an ethanolic extract from Elettaria cardamomum pod (ECPE) as a corrosion inhibitor for Mild Steel (MS) in 1 N Hydrochloric acid (1 N HCl) electrolyte was investigated via gravimetric analysis and electrochemical studies like Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) studies. Qualitative technique such as Gas Chromatography-Mass Spectrometry (GC–MS) was used to identify the main phytochemical components of the ECPE, such as phenolic chemicals, tannins, flavonoids, amino acids, carbohydrates, proteins, and terpenoids. With increasing in inhibitor concentrations (50-250 ppm), it was discovered that the efficiency of the inhibition increased to a maximum inhibition of 60.6% with 250 ppm at 303 K after 1hr. The influence of four distinct temperatures (303-333 K) were also examined where the inhibition efficiency decreased with temperature. The inhibitors were adsorbed onto the MS surface via physisorption. The adsorption of inhibitor appears to function through Freundlich adsorption isotherm more appropriately. EIS study showed that the values of resistance due to charge transfer (Rct) increased with concentration of ECPE where the PDP plots indicate that the extract functions as a mixed inhibitor affecting both the anodic and cathodic partial reactions of the corrosion process. Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FT-IR), and Atomic Force Microscope (AFM) investigated the surface morphology and topology of the MS which confirmed the adsorption of inhibitor molecules on the metal surface. The contact angle method predicted the hydrophobic nature of the MS in the presence of inhibitor. The results of Ultraviolet-Visible Spectroscopy (UV-Vis) provide evidence of iron/inhibitor interaction, which is responsible for the inhibition of corrosion. From all these investigations, it can be concluded that the ECPE acted as a good corrosion inhibitor for MS in a 1 N HCl electrolyte.