Exploration of the Funaria hygrometrica extract as an eco-friendly corrosion inhibitor for X60-steel in HCl media

The Funaria hygrometrica extract (FHE), prepared using a planet ball-milling method with distilled water at room temperature, was studied as an eco-friendly inhibitor with high anti-corrosion performance for X60 steel in HCl solutions. FTIR analyses were conducted to track the active components of the Funaria hygrometrica extract. The anti-corrosion performance of the FHE was investigated using systematic electrochemical tests and morphological examinations, and the results manifest that the FHE is a mixed-type inhibitor with an inhibition efficiency of 93.12% at 293 K in the presence of 500 ppm, which is due to their adsorption films on steel surfaces, isolating the substrate from the aggressive environment. Surface analyses and adsorption isotherm studies were combined to explore the anti-corrosion mechanism of the FHE on steel substrate surfaces in detail. The results of XPS measurements indicate that the FHE absorbed onto steel surfaces, forming a N-Fe bond. The adsorption model studies demonstrate that the adherence of the FHE at the steel/solution interface complied with the Langmuir adsorption isotherm, and there was an interactive force between FHE molecules. Additionally, theoretical calculations were performed to further understand the adsorption and inhibition mechanism of the FHE.