Extracts from plant materials have great potential as alternatives to inorganic corrosion inhibitors, which typically have harmful consequences. Experimental and theoretical methodologies studied the effectiveness of agricultural waste, namely, date palm seed extract as a green anti-corrosive agent in 0.5 M hydrochloric acid. Experimental results showed that immersion time and temperature are closely related to the effectivity of date palm seed as a corrosion inhibitor. The inhibition efficiency reduced from 95% to 91% at 1400 ppm when the immersion time was increased from 72 h to 168 h. The experimental results also indicated that the inhibition efficiency decreased as the temperature increased. The presence of a protective layer of organic matter was corroborated by scanning electron microscopy. The adsorption studies indicated that date palm seed obeyed Langmuir adsorption isotherm on the carbon steel surface, and Gibbs free energy values were in the range of −33.45 to −38.41 kJ·mol−1. These results suggested that the date palm seed molecules interacted with the carbon steel surface through mixture adsorption. Theoretical calculations using density functional theory showed that the capability to donate and accept electrons between the alloy surface and the date palm seed inhibitor molecules is critical for adsorption effectiveness. The HOMO and LUMO result indicated that the carboxyl (COOH) group and C=C bond were the most active sites for the electron donation-acceptance type of interaction and most auxiliary to the adsorption process over the Fe surface.
In this work, the corrosion inhibiting properties of date palm seed extract (DSE) for carbon steel in 0.5 M hydrochloric acid (HCl) solution has been investigated using several techniques, including weight loss measurement, potentiodynamic polarisation (PDP), and electrochemical impedance spectroscopy (EIS). By adding the DSE concentrations in 0.5M HCI solution from 800 ppm to 2000 ppm, the inhibition efficiency (IE%) was improved with DSE concentration up to 1400 ppm. Highest IE% of 94 in weight loss, 92 in PDP, and 97 in EIS were all attained at an optimum DSE concentration of 1400 ppm. Further increasing the DSE concentration to 2000 ppm, IE% was shown to be decreased. Moreover, the PDP measurement indicated that DSE is a mixed-type inhibitor, affecting both cathodic and anodic partial reactions. From the Gas Chromatography and Mass Spectrometry (GC-MS) analysis, it was revealed that DSE is mainly composed of (wt.%) 36.0 lauric acid, 12.0 caprylic acid, and 10.7 myristic acid. This study revealed that DSE has it could serve as a green corrosion inhibitor for carbon steel in HCl medium.
The inhibition effects of the date palm seed extract corrosion of mild steel in 0.5 M HCl at different concentrations are investigated by potentiodynamic polarisation (PDP), electrochemical impedance spectroscopy (EIS) and weight loss tests. Additionally, this study provides a fundamental understanding of aromatic adsorption on iron (Fe) surfaces. Furthermore, the surface morphology and the extracts are performed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The maximum inhibition efficiency of 95, 96, and 91% were realised at 1400 mg/L for PDP, EIS, and weight loss, respectively. The inhibitive action of the DPS extract against mild steel corrosion in an acid solution has been supported by SEM analysis. The FTIR showed that the extract contained hydroxyl (−OH) and methoxyl (−OCH3) functional groups. The DFT depicted the adsorption sites at the oxygen (O) and carbon (C) atoms as deduced from the Fukui functions, Mulliken atomic charge, and the highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO) analysis. The DPS preferred to form chemical bonds by donating electrons to the Fe surface. The coordinate bonds between the O and C atoms and the metal surface resulted in a high inhibition efficiency value. In conclusion, date palm seed extract is an effective inhibitor to protect mild steel from corrosion in an acidic medium.
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