A green Brassica oleracea L extract as a novel corrosion inhibitor for Q235 steel in two typical acid media

Abstract Based on the eco-friendly, sustainable, and high-efficiency themes, an aqueous extract of Brassica oleracea L (BOLE) was employed to retard Q235 steel corrosion in two harsh acid environments (0.5 M H2SO4 and 1 M HCl) for the first time. The ingredient and corrosion inhibition ability of BOLE had been testified via Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-vis), conventional and in-situ electrochemical techniques, surface topography research, and X-ray diffraction (XRD). The experimental results showed that BOLE was a mixed-type inhibitor and possesses superior inhibition ability due to the compact BOLE protective film. The inhibition efficiency was 92.3% in H2SO4 and 93.8% in HCl when the added dose of BOLE was merely 300 mg/L. Meanwhile, the chemical adsorption reaction of the BOLE/steel surface was demonstrated by the N‒Fe bond from X-ray photoelectronic spectroscopy (XPS). In theoretical calculation, the calculated values of low energy gap (ΔE) and high dipole moment (μ), as well as Ebinding in neutralization and protonation conditions related to powerful interaction between BOLE and steel, which also revealed the excellent anti-corrosion ability of BOLE at the micro-level.