Falcaria vulgaris leaves extract as an eco-friendly corrosion inhibitor for mild steel in hydrochloric acid media

Abstract

Undoubtedly, metal corrosion is one of the most challenging problems faced by industries. Introducing corrosion inhibitors is a reasonable approach to protecting the metal surface. Due to environmental concerns and the toxicity of industrial organic corrosion inhibitors, researchers are continually exploring acceptable replacements. The current study focused on the application of Falcaria Vulgaris (FV) leaves extract to mitigate mild steel (MS) corrosion in a 1 M HCl environment. The polarization findings demonstrated that the corrosion current density decreased from 264.0 µA/cm² (for the sample submerged in the blank solution) to 20.4 µA/cm² when the optimal concentration of 800 ppm of FV leaves extract was added to the acid solution. Electrochemical impedance spectroscopy (EIS) analysis revealed an inhibition efficiency of 91.3% at this concentration after 6 h of immersion. It was determined by analyzing several adsorption isotherms that this corrosion inhibitor obeys the Frumkin isotherm. AFM, FE-SEM, and GIXRD surface analyses also supported the findings that adding FV leaves extract can reduce metal damage by adsorption on the metal surface.

Figure 1

The chemical structure of Carvacrol (a), Spathulenol (b), Genistin (c), Rutin (d), Quercetin-3-O-glucoside (e), and Quercetin (f).

Figure 2

OCP vs time diagrams for MS submerged in an acidic solution without and containing different concentration of FV leaves extract.

Figure 3

Nyquist (left) and Bode (right) plots of MS soaked in 1 M HCl solution without (a,b) and containing 400 (c,d), 600 (e,f), 800 (g,h), and 1000 (i,j) ppm of FV extract.

Figure 4

The corrosion inhibitor adsorption process: at optimum concentration (a) and above optimum concentration (b).

Figure 5

Polarization curves of MS submerged in blank and inhibitor-containing solutions.

Figure 6

Frumkin (a), Temkin (b), Freundlich (c), and Langmuir (d) adsorption isotherms diagrams.

Figure 7

Schematic of the proposed mechanism of adsorption of FV leaves extract on MS surface.

Figure 8

FE-SEM images of MS surface soaked in acidic solution without (a₁, a₂) and with 800 ppm FV extract (b₁, b₂).

Figure 9

AFM micrograph of MS surface in 1 M HCl without (a) and with 800 ppm FV extract (b) after 6 h of immersion.

Figure 10

FTIR spectrum of the FV powder and MS immersed in the acidic solution containing 800 ppm FV extract after 6 h of immersion.

Figure 11

UV–Vis spectra of 1 M HCl solution containing 800 ppm FV extract before and after MS immersion.

Figure 12

GIXRD patterns of the MS surface immersed in 1 M HCl (a) and 1 M HCl solution containing 800 ppm FV extract (b) after 6 h of immersion.