Precise major compounds in Barringtonia acutangula flower - water extract for mitigating carbon steel corrosion

Background: Plant extracts have been recognized as prospective and sustainable alternatives with the advantages of high efficiency, eco-friendliness, abundant sources, and ease of regeneration. Even though specific techniques have been applied to identify the major compounds in plant extracts, their values on corrosion inhibitors are still questionable.Methods: The major compounds in Barringtonia acutangula flower-water extract (BAFE) were first isolated and quantified via various chromatography techniques such as chromatography column and high-performance liquid chromatography (HPLC) method, respectively. The density functional theory (DFT) was used to confirm the electrochemical properties of these compounds and the molecular dynamics (MD) investigated the BAFE film/ substrate interactions. Electrochemical techniques were used to study the steel's anticorrosion ability of the extract in 1 M HCl solution. After being immersed to the investigated solution, the sample surface was examined for morphologies, components, and the elemental distribution using various surface analysis techniques (Scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy). Significant findings: This study offered a new method to determine the precise major components in BAFE, including ilexsaponin A1 and gallic acid. In addition, DFT and MD simulations indicated that these compounds performed chemisorption on steel surfaces with good adhesion, thermal stability, and enriched electron density. These properties ensure the formation of a smooth protective layer on the steel surface. Potentiodynamic polarization data indicated BAFE as a mixed-type of corrosion inhibitor with a dominating cathodic process. When BAFE concentrations increased from 0 to 3000 ppm, the inhibition performance increased and reached the highest inhibition efficiency of 95.57 % at 3000 ppm. As the concentration further increased to 4000 ppm, the inhibition performance decreased. This can be attributed to the low vivaciousness of organic species in the solution that hinders the absorption process of the protective film on the steel surface.